(Answered UPDATED) Resolving collisions during a skid

[Alfaryn]

Three problems related to resolving collisions during a skid:

1. Both pp. 62-63 TW (Buildings and Other Units sections) and pp. 70-71 BMM (Collisions with stationary objects and Collisions with 'Mechs sections) seem to agree that if a skidding unit successfully unintentionally charges another unit, charge damage to the target is calculated based on hexes moved by the attacker before the skid started. There are however no such statements for damage taken by building hexes units skid into. Is this an oversight, or should we add hexes a skidding unit moved before and after a skid to determine damage done to a building in such situation?

2. The first paragraph of Collisions with 'Mechs on p. 71 BMM says to resolve any falling and skidding damage "up until the crash [...] before resolving any part of a collision with a 'Mech", which coupled with the placement in the section (before a paragraph that says how to determine if the unintentional charge was successful) seems to suggest that if a skidding 'Mech enters a hex occupied by another 'Mech, the falling and skidding damage accumulated up to this point should be resolved even before checking if the collision between the 'Mechs accrued. This interpretation seems to be supported by the example text on p. 69 BMM and the second full paragraph on p. 65 TW.

However none of the rules on pp. 62-63 TW say to apply falling and skidding damage before checking if a collision between units happened instead the second paragraph of the Collisions section says to apply such damage before any damage from a collision. I assume that is an oversight that needs to be corrected?

3. I realize that this may be nitpicking, but the "It suffers normal falling damage and then skids" at the end of the second paragraph of the skidding section on p. 62 and at the end of the first paragraph on p. 68 BMM could be changed to let the players know in that sentence that the fall damage in such situation is resolved together with subsequent skidding damage? I realize that the following paragraphs say exactly that, but I fear that some players seeing the rarely used and difficult to remember wall of text that are skidding rules may try to break up the task by resolving the falling damage first and reading what the subsequent rules say later.

Perhaps changing the sentence in question to something like "It suffers normal falling damage (which is not resolved immediately, however - see below) and then skids" would make the rules easier to understand before any damage incorrectly ends up on 'Mech sheets?

[Xotl]

1. The wording should be "Use the distance the skidding unit moved this turn prior to the crash (both before and during the skid) to calculate damage."

2. The intent is to resolve skid damage for the hexes prior to the collision prior to making any rolls involved with the collision, and damage caused by additional hexes skidded afterwards, after the collision damage is resolved.  I'll clean up the wording to make that clear in the rules.

3. You resolve the fall, and only then do you skid.  The fall entirely happens first, before you even begin to resolve skidding.

[Alfaryn]

I can see a couple issues with your answers Xotl:

Ad 1. Is this answer only for collisions with buildings and similar stationary objects, or also for collisions with other units? I'm asking because if it is the latter, then it explicitly contradicts both the rules for collisions with units as they are written now (second paragraph on p. 63 TW and the third paragraph of Collisions with 'Mechs on p. 71 BMM) and the example in TW (p. 65, the paragraph beginning with "The skidding unit strikes[...]").

Ad 3. This answer also seems to contradict both the rules and the example text in TW as they are written now (third paragraph on p. 68 BMM, third paragraph of the skidding section on p. 62 TW, paragraph beginning with words "Because the target[...]" on p. 65 TW). It is not entirely clear if the answer also contradicts the second paragraph of the example on p. 69 BMM, because in that example the skidding Phoenix Hawk suffers 5 points of falling damage which just happens to be one full damage grouping used while resolving falling and skidding damage, but since the the example calls for resolving both falling and skidding damage after stating that a collision may happen, but before there before rolling to see if it does, I would say that the intent here also seems to be that you add up all falling and skidding damage first, and then resolve the summed up damage as 5-point value groupings.

I'm not saying that your answers are wrong, but if they aren't, then the rules and examples mentioned above in this post need to be corrected as well.

Other than that, thank you for prompt response.

[Xotl]

I'll take a fresh look at this next week.  Thanks for the feedback.

[Xotl]

Okay, take a look at this updated TW text if you please.  I hope it resolves points 1 and 2 without invalidating any examples.  I'll clean up 3 separately.

https://www.dropbox.com/scl/fi/hg6cz8xzzycs5awweazp0/TW-Collision-Replacement-Text-11th-printing.docx?rlkey=msxlai5cxqd2xe84rj524x3fx&dl=0

[Alfaryn]

The changes look good to me for the most part, but:

1. First sentence of the second paragraph of the "Collisions" section:

Before if a collision occurs or any damage from it, first resolve [...]
change to:
Before checking if a collision occurs or any damage from it, first resolve [...]

You may also drop the word "first" from the sentence, and perhaps add something like "applying" before "any damage from it".

2. Last sentence of "Buildings" section. "In either case [...] the skid ends, [...]" does not mesh well with the previous sentence which describes a situation in which the skid does not end. Moreover one of the cases described (the one when the building does not collapse due to collision) is already covered earlier in the section.

Perhaps the best way to fix this would be to remove the last sentence in the section entirely and change the last sentence in the second paragraph of the section to something like:

After subtracting, if there are still hexes to be skid, the skid continues, if not - the skid ends, with the skidding unit now occupying the building hex.

3. "Buildings" section says how much damage is dealt to a skidding unit that collides with a building, but not how to determine damage value groupings and unit locations the damage is applied to.

4. "Other Units" section says to apply collision damage to the skidding unit using Front/Rear column, but does not make it entirely clear if a skidding unit may take damage to its rear armor, or if it is always treated as taking damage to its front regardless of its facing relative to the direction of the skid.

5. Nitpicks:

- "the unit’s skidding ends" in the second paragraph of the "buildings" section does not sound natural to me. Perhaps "the unit's skid" or just "the skid" would be better?

- "Distance the skidding unit moved this turn prior to the crash (i.e. not counting skidding hexes)" appearing twice in the text sound a bit unfortunate due to how word "move" may or may not cover things like skids, sideslips displacements etc., but admit I'm not sure how to replace it. Would "distance the skidding unit moved this turn prior to the skid" be better? Or would be too likely to be misread or misinterpreted by some people?

Note that most of the above points apply to current BMM rules as well.

[Xotl]

1. It needs to be a bit clumsy because there's two situations it must cover: an auto-collision (buildings) and a possible collision (units).  But what you're quoting was garbled and so I've adjusted further.

2. Yes, that example of skidding into buildings is odd.  It's straight from TW, but must be wrong since it says the unit stops skidding even if it destroys the building and has skid MP left.  I've altered it in the replacement text.

3. Lets go with the same damage allocation rules for Levels, for consistency's sake.

4. If there's no caveat, then that would include the possibility of rear hits.  I don't think it's possible to skid into something via your rear though, since you have to be running and you can't run backwards, and you skid in the direction you were going before the skid.

5. Made some small adjustments, but I want to keep the parenthetical on not counting skidding hexes to reinforce that part.

Sample text updated.  Thanks for the help as always.

[Alfaryn]

Re. 4 - the way I see it you can skid front, rear or any side first. Remember that a skids (or a sideslips, which use most skid rules) happen after units turn, but before they enter a new hex. I can imagine for example a hovercraft that wants to end its movement phase close to the place it started, but generate a high TMM by going forward a few hexes at flank speed, turning 180 degrees, and coming back to or close to the hex it started in. If it fails its PSR after the 180, it will "sideslip" in its original movement direction rear first. Skidding 'Mechs are even more unpredictable, since as soon as they start skidding they fall, and I don't see any exception in the rules saying that you shouldn't randomize their facing after fall as normal. In fact the third paragraph of Skidding section on p. 62 TW seems to suggest the opposite.

I would consider it most realistic to use the column of hit location table appropriate to direction of a skid relative to skidding unit's facing (for example Right Side of a 'Mech that is sliding in a direction two hex sides right from its facing), but can accept other rulings (only Front or only Front except when sliding rear first) for simplicity's sake if nothing else. In any case though, the rules need to be clear which side to use in any combination of skidding unit's facing and skidding directions, because any combination of the two are possible.

However you end up ruling about determining direction of damage taken by a skidding unit that crashes into another unit, I think that, for consistency's sake, direction of damage taken by a unit that skids into a building should be determined the same way.

Other than that, the updated rules text seems fine to me.

By the way, are landed DropShips considered unusual targets for the purposes of determining if an unintentional charges hit them? I guess they should have some special rules either about being hit by unintentional charges or by charges in general to avoid weird situations where a 'Mech skids into a center hex of a landed dropship after missing one of its outer hexes. You may want to clarify it on p. 148 TW, where DropShips are mentioned as unusual targets in the Damage section, but not in the part of the rules about determining if a charge hit in the first place.

[Xotl]

Good point on Dropships: I don't think the current skid and charging rules properly handle them at all.  I'm thinking two parts are required here:

1) A new section under skidding just for Dropships.
2) A note to p. 148 to clarify that DropShips are not displaced after a charge, and instead both units stay where they are.

Also, the Buildings skid section now says that damage is based on the charge direction, just like Levels.  Proposed text updated again.

[Alfaryn]

Considering that landed DropShips may be targets of DFA attacks, unintentional falls from above, have units displaced into them either through direct physical attacks or through domino effects, the statement that both a DropShip and a unit that would be displaced into its hex stay where they are should probably be added in Unit Displacement section on p. 151 (possibly around the fourth paragraph that handles displacements into illegal hexes), not on p. 148. Would just saying that for purposes of displacement all hexes (and possibly elevations) occupied by landed DropShips are considered prohibited terrain be enough?

If damage taken by a unit skidding into building hex is resolved using the general attack direction rules on p. 119, then I think that the same should apply to units skidding into other units, which requires an appropriate change in the first sentence of the second paragraph of Other Units section of the proposed collision rules.

[Xotl]

Charges have a displacement quality but are not themselves a purely displacement action, if that makes any sense, and so a reference on p. 148 is necessary.  However, I can squeeze one into p. 151 as well, to deal with related situations (treat them as prohibited terrain).

I don't want to change the Other Units damage direction because TW specifies how that is supposed to work already: it specifically says Front/Rear always, and this rewrite is supposed to patch holes, not change existing material.  If I was doing it from scratch I would almost certainly sync collisions with Levels, Units, and Buildings better and use true direction for all of them (but then again, if I was doing it from scratch the first thing I would do is light the skidding rules on fire).

What I hope is the final draft is now up.

[Alfaryn]

Fair enough, though if you keep the Front/Rear column for resolving damage to skidding units that skid into another units, you really should specify if the damage is always applied to the front, or either to the front or rear depending on direction of the skid relative to facing of the skidding unit, and if it is the latter - which side is used when. For example if a unit is skidding in a direction 120 degrees or two hex sides away from its facing, does it take the damage to its front or rear?

[Xotl]

Will do.  Thanks a ton for the help on this one: it will all go in to the next BMM and TW prints.

[Alfaryn]

Sorry for more nitpicking, but I decided to give the proposed rules one more look, and I think there are two more things that you can do to make them more clear:

1. In Buildings section there is a sentence "Treat the attack as if it came from the hex that the skidding unit crashed into." The problem with it is that if I interpret the rules correctly a skidding unit enters a building hex first, and only then resolves the crash (unlike when crushing into levels). This means that technically the proposed rules say that the unit takes damage from a hex it is already in, which in turn makes it unclear how you are supposed to determine attack direction/hit location table column, or that the rule in question has anything to do with attack direction at all. Perhaps change "the hex that the skidding unit crashed into" to something like "the direction the unit was skidding towards" and/or add a reference to Attack Direction section on p. 119 TW/32 BMM?

2. In the Levels section you may want to change "the skidding unit automatically crashes into it and stops" so it is perfectly clear that the skidding unit is supposed to stop one hex short of entering a hex it crushed into - both to make it perfectly clear where the unit is supposed to end its movement and to make it clear that "Treat the attack as if it came from the hex that the skidding unit crashed into." in the same section refers to incoming attack direction. On top of that perhaps similarly to point 1. changing "from the hex" in the sentence I've just mentioned to something like "from the direction of the hex" could make things even less likely to misinterpret.

Once again sorry for bombarding you with minor suggestions the rules may not even need at this point, and thank you for all your work here.

[Xotl]

No problem.  I've made some slight adjustments to the text to take your comments into account.

[Alfaryn]

Dammit, one more thing - in the Other Units section:
(round fractions up, always applied to the front unless the skidding unit is facing the rear, in which case use the rear)
"Facing the rear" of what exactly? I believe it would be better to just say that the skidding unit is "facing directly away from the direction of the skid", "skidding directly backward", or something similar.

Edit: Scratch all of the above? It may be irrelevant in light of what I'm about to say below.

I've just looked at the current errata document for TW, and it looks like the rule that damage from crashing into Levels based on direction of the skid relative to facing was introduced in fifth printing. Before the rules said to use the Front/Rear columns - just like they currently say for crushing into other units. Looks like originally the intent of the rules was that hit locations for skidding unit were supposed to be determined the same way regardless of what it collided with, and they just did not explicitly say that in the buildings section.

I think this is a strong argument to make the rules internally consistent again by making it so no matter what a skidding unit collides with, the method of determining hit table column is the same. I don't know what the reasoning for the change to resolving collisions with Levels in fifth printing was, but I strongly suspect it would apply to collisions with buildings and units as well, and it was just missed then that it needs to be applied to collisions with buildings and other units as well. After all, if we always use Front/Rear column (or columns in case of Vehicles) we get situations where for example a tank crashing while skidding to the left may damage its right side, but not rear - weird regardless of what the tank is crashing into.

Whichever method of determining a hit location table column you choose, as long as you decide that it should be the same regardless of what a skidding unit crashes into, I think the rules for that may be safely moved from Buildings, Levels and Other Units subsections to the general rules for collisions - right next to a statement that all skidding and collision damage should be applied in 5-point value groupings.

Edit 2: Yet another nitpick. Considering that during collisions with other units you resolve collision damage first, and unit displacement due to unintentional charge second (unlike collisions with buildings), the rules should probably specify if a skidding 'Mech should resolve skidding damage for entering a hex previously occupied by a unit it intentionally charged (assuming both units survived the charge, otherwise it is obvious that you should), and whether the skidding damage for entering a hex in which the crash occurred should happen before or after the damage taken by the skidding unit due to unintentional charge.

[Xotl]

<snip>

I think this is a strong argument to make the rules internally consistent again by making it so no matter what a skidding unit collides with, the method of determining hit table column is the same.

Whichever method of determining a hit location table column you choose, as long as you decide that it should be the same regardless of what a skidding unit crashes into, I think the rules for that may be safely moved from Buildings, Levels and Other Units subsections to the general rules for collisions - right next to a statement that all skidding and collision damage should be applied in 5-point value groupings.

After further reflection I have done that.  I had already made that generalist section for TW, but I had to create a new section in the BMM to do that there, which took a bunch of surgery, but I think it works.  TW draft is updated; I'll be posting a BMM draft shortly once I deal with whatever the bottom note is.

Edit 2: Yet another nitpick. Considering that during collisions with other units you resolve collision damage first, and unit displacement due to unintentional charge second (unlike collisions with buildings), the rules should probably specify if a skidding 'Mech should resolve skidding damage for entering a hex previously occupied by a unit it intentionally charged (assuming both units survived the charge, otherwise it is obvious that you should), and whether the skidding damage for entering a hex in which the crash occurred should happen before or after the damage taken by the skidding unit due to unintentional charge.

At this point I've been staring at these pages for days and my brain is tapioca.  Could you be more specific here, perhaps with an example and using the current draft wording/section order?

[Alfaryn]

I hear you about the tapioca. We are on what, 7th version of the rules draft? I just hope that we somehow do good enough job here that we won't ever have to deal with correcting skidding rules again.


Let's see if I can explain better what I meant in edit 2. To make it easier I'll underline the issues that could use clarification in the rules text.

Let's assume a 'Mech falls in hex X, skids through a clear, empty hex Y, and runs into an obstacle in hex Z. How much damage does it take? The way I see it, it depends on what the obstacle is:

A. If it is a hill or a DropShip, the skid ends in hex Y, and the 'Mech first takes fall and 1-hex skid damage, and then collision damage as described in Levels or DropShip sections.

B. If it is a three or more levels drop, then the 'Mech suffers fall and I believe 1-hex skid damage, and then another fall damage as described in Accidental Falls from Above section on p. 63 TW. The skid ens in hex Z.

By the way, the rules are not entirely clear if the unit should suffer skidding damage for entering hex Z in this case. I assume not, because the way I imagine it the unit falls into that hex, not slides along the ground there. You may want to clarify it in the section mentioned above.

C. If the obstacle is a Building the 'Mech enters hex Z first, takes fall and 2-hex skid damage, then collision damage with a building, and if the building collapses the 'Mech suffers damage because of it as well, and a skid may continue leading to further damage down the line.

D. If the obstacle is a unit other than a DropShip or large Vehicle, then the rules say to first resolve damage from initial fall and the skid so far, and then check if the collision occurs. Since during charge attacks to-hit rolls happen before any displacement I assume this initial damage to the skidding 'Mech is for fall and 1-hex skid, because at that point the skidding unit is still in hex Y, not Z, though it would be nice if the rules clarified that, since the collision may "feel" like it happens in hex Z. After that:

  - if the unintentional charge misses or destroys the target unit while suffering the collision damage itself, the skid continues as normal,

  - if the intentional charge hits and fails to destroy the target and the unit, and no displacement may happen afterwards (for example due to Prohibited Terrain behind the target unit - see Location after Attack section on p. 148 TW), skidding 'Mech suffers the collision damage, and stays in hex Y suffering no more skidding damage,

  - if the intentional charge hits and fails to destroy the target and the unit, and both the skidding 'Mech and its target are displaced 1 hex, the 'Mech obviously suffers collision damage, but does it suffer skidding damage for being displaced from hex Y to hex Z? On one hand I think it shouldn't because I believe post-charge displacement is not the same as a skid as far as the rules are concerned, and because there are situations when a prone 'Mech can be displaced (most of them completely unrelated to skids), and the 'Mechs don't suffer skidding damage in these situations. On the other hand the post-charge displacement certainly looks a lot like a pre-colision skid, so the players may be inclined to treat it as a 1-hex continuation of the skid, and resolve the damage...

To sum it up, if my interpretation of the rules is correct I think you should:

1. at the beginning of the Other Units section make it clear that before checking if the collision occurred a skidding unit doesn't suffer skidding damage for entering the hex with the target of unintentional charge, because at that point it hasn't entered this hex yet,

2. make it clear in or around the "Otherwise, adjust both units’ positions on the map as for a successful charge, and the skid ends" sentence in Other Units section that the post-charge displacement doesn't cause any skidding damage.

3. in Accidental Falls From Above section on p. 63, you should make it clear if the hex containing 3+ level drop into which a skidding 'Mechs falls counts for calculating skidding damage or not. (I believe it shouldn't, but I'm less certain about this then the other points).

Perhaps a well phrased clarification in point 2. may even make the one I suggest in point 1. unnecessary?

Edit: In case it wasn't clear, the thing in points D, 1 and 2 is what I meant to point out in Edit 2 of my previous post. The issue in points B and 3 is new.


Aside from that I've taken a look at Sideslipping rules, and unfortunately noticed a couple disparities between these rules and the skidding rules that may need to be addressed:

I. According to the rules of Buildings, DropShips, Large Support Vehicles and Levels section on p. 68 a sideslipping unit "[...]automatically charges the unit or building hex[...]". I think that this sentence should clarify that to calculate charge damage should count only hexes traveled by the charging unit before the start of the sideslip (analogically to how the damage is calculated for unintentional charges during a regular skid).

II. According to Buildings, DropShips, Large Support Vehicles and Levels section on pp. 67-68 all four of these kinds of obstacles cause an automatic crash (without a to-hit roll). This may mean that if a skidding unit runs into a Large Support Vehicle (LSV), the collision is also automatic (though unlike collisions with the other kinds of obstacles mentioned in this section, I believe it could still cause post-charge displacement, and he damage to the attacker would be calculated using target's tonnage as normal). On the other hand regular attacks (including intentional charges) against Large Support Vehicles just get a -2 to-hit modifier, and Accidental Falls From Above get a -3 to-hit modifier to hit a Large Support Vehicle, so perhaps such collisions shouldn't be automatic? The rules seem to be all over the place when it comes to charges, collisions, and such with LSVs, so I don't know which, if any, of them should be changed, though... below are a few thoughts about possible consequences that are either potentially unwanted or may need clarifications in the rules.

IIa. If collisions with Large Support Vehicles during skids and/or sideslips are automatic, then what if it is an LSV that is skidding/sideslipping? Would it automatically hit any other units along the path of the skid?

IIb. If collisions with Large Support Vehicles during skids and/or sideslips aren't automatic, and after missing an unintentional charge a skidding unit would end its skid in LSV's hex the LSV would get displaced as per normal rules on p. 151, right? What if it can't be displaced due to prohibited terrain for example? Does the skidding unit return to the hex it came from, but if it is a 'Mech it still suffers skidding damage for entering a hex with the LSV?


Finally I've noticed a minor typo in the fourth paragraph of the draft - one space too many before "For the purposes of calculating attack direction,[...]" sentence.

[Xotl]

By the way, the rules are not entirely clear if the unit should suffer skidding damage for entering hex Z in this case. I assume not, because the way I imagine it the unit falls into that hex, not slides along the ground there. You may want to clarify it in the section mentioned above.

I had noticed that yesterday while going through the BMM examples on skidding.  I'd already edited the BMM section to specifically call out what the example later shows, which is that you don't take damage for skidding into air.  I'm not sure if I can get that into TW, however, due to space issues, but I'll see (and in any case it won't be in the area covered by the rewrite document below).

Otherwise, I've updated the drafts to clarify precisely how you handle fall & skid damage to the point any given collision type occurs.  Here's the TW one again, and the BMM one:

https://www.dropbox.com/scl/fi/hg6cz8xzzycs5awweazp0/TW-Collision-Replacement-Text-11th-printing.docx?rlkey=msxlai5cxqd2xe84rj524x3fx&dl=0
https://www.dropbox.com/scl/fi/5qsgoipsgx2htdkfdb7n7/BMM-Collisions-pp.-70-71.docx?rlkey=9347kvz8dy6qj6n3jmtyos1j7&dl=0

[Alfaryn]

Both books:

1. Since fall and skidding damage is resolved at the end of the skid, but represents damage taken along the entire path, Water section on p. 63 TW and p. 70 BMM should specify if this damage causes hull breach checks (see Underwater Units p. 121 TW / Hull Integrity and Breaches p. 43 BMM).

2. Moreover Water sections mentioned above say that "No additional damage is applied in this case" / "This entry into water does not deal additional damage". This is a bit unclear - does it mean that the fact of entering water during a skid results in no extra damage outside of what other rules specify, or does it mean that a skidding 'Mech doesn't count the water hex for purposes of calculating skidding damage? I assume that if water is deep enough for Accidental Falls From Above rules to apply, the skidding unit would still suffer the fall with appropriate damage (halved per Falling Damage section on p. 57 TW / Water section on p. 57 BMM), with normal hull breach checks. Something to clarify in the rules, space permitting of course...

3. The rules for collisions with Other Units/'Mechs point the reader at Unit Displacement/Location After Charge rules, but make no mention that if a charge misses, and the skid happens to end in the hex with Other Units/'Mechs, the players may still need to use (Unit) Displacement rules if Stacking limits are exceeded. This is obviously a low priority thing, but if there is some space left after all other corrections, it would be nice to remind the reader that Stacking limits apply in such situation (and provide reference to p. 57 TW / p. 18 BMM).


TW:

4. The draft still doesn't clarify if a 'Mech that unintentionally charges another unit suffers skid damage for post-charge displacement, though if space is a concern, then hopefully it shouldn't be that difficult for most players to figure out that it doesn't.

Do I correctly assume it doesn't?

5. In the DropShip's section "Resolve a collision as if the DropShip were a building (see above). However, calculate damage to the skidding unit using its own tonnage, rather than the DropShip’s." technically works, but sounds weird, because damage to skidding units that hit buildings obviously doesn't use building's tonnage either. Could it be phrased better?

6. I assume that Accidental Falls From Above is still supposed to be right below Levels section? It really should be there to avoid reader's confusion. Either move Accidental Falls From Above section between Levels and Other Units sections, or (better in my opinion) put Levels section below Other Units section, like it is in the current printing.

7. Unlike its BMM counterpart, Buildings section in the TW draft doesn't mention interactions between skidding units and basements. Is this an error, or just an omission due to lack of space?

8. I need to correct my statement from a few posts before - per current TW rules (p. 149) airspace units (including DropShips) can't be a target of DFA attack, so no mention that a DropShip can't be displaced by such attack is needed. Though it makes me think if this isn't an error, and the rules were supposed to say that you can't DFA airborne airspace units. Another thing is that if I understand the recent changes to physical attacks against underwater units make it so you can never DFA any underwater unit (not only submerged Naval Vessel) so perhaps "Submerged Naval Vessels and Aerospace Units" paragraph on p. 149 should be renamed to something like "Fully Submerged Units and Aerospace Units" or "Fully Submerged Units and Airborne Aerospace Units"? The latter title would of course require a note on in Location After Attack section on p. 150 that successful DFAs can't displace landed DropShips, and instead both attacker and defender stay where they were before the attack was resolved.

I realize that such DFA issues are a bit off topic here. Should I start a separate thread for them?

9. I assume that the Sideslipping rules issues I've mentioned in the previous post will be addressed in the upcoming printing? I think that at least the one in point I. should be.


BMM:

10. To avoid reader's confusion the rules in the Collisions - General section should start by shortly explaining to the reader what a collision is, and when it may occur. Currently neither this section nor a preceding Interrupting A Skid section does it adequately. In my opinion adding the following sentence at the beginning of the Collisions - General section should be sufficient: "If an obstacle (e.g. a building, a 'Mech, a hill) lies in the path of the skid, the skidding unit may crash into it."

11. Collisions paragraph in Interrupting A Skid section on p. 70 refers to Collisions rules on p. 70... Perhaps change "(see p. 70)" to "(see below)"1

[Xotl]

1. If you enter water your skid is done, and it already says you check for hull breaches in that case.

2. I have no idea what the original intent was with that passage, so I'm just going to change it.

3. I try to avoid "yes, the normal rules still apply" passages unless the situation is extremely confusion and thus calls for it.  I doubt I will have the room in any case.

4. Displacement isn't a skid and so doesn't cause skid damage.

5. Changed.

6. The rest of the passage is there as normal: only what is being edited is in the document.  However, there is something I want to adjust there now so I added it in to the latest draft.

7. Probably dealt with elsewhere.  If it's not there now it's certainly not being added, as the section may require a font shrink as it is to get everything in.

8. Not dealing with this here.

9. Not dealing with this here.

10. Good point; done.

11. Already fixed: there's a bunch of small-scale changes to earlier in the section as well, including a big rewrite to some of p. 68.

Cheers.

[Alfaryn]

1. The rules on p. 70 BMM remind the player (perhaps needlessly) that a section with armor stripped completely automatically suffers a breach. The point that I was trying to make however was that it is unclear if you should roll for a possibility of a hull breach for non-armor-penetrating damage value groupings while resolving fall/skidding damage if a skid ends in a Depth 1+ water hex. Remember that whenever you take non-armor-penetrating hit underwater, you roll 2d6, and on 10+ you suffer a breach despite still having armor on the section.

4. Perhaps the simplest way to make the point across is to change the order of events in the relevant sentence? Instead of "Otherwise, the target unit is displaced into the adjacent hex in the direction that the attacker skidded into it (see Unit Displacement, p. 151) and the skid ends." write "Otherwise, the skid ends and the target unit is displaced into the adjacent hex in the direction that the attacker skidded into it (see Unit Displacement, p. 151)."

5. "However, do not include the DropShip hex in the damage calculations, [...]" fragment only confuses the reader in my opinion. You can simply delete it, because the general rules for skidding already say that unintentional charge damage calculation only counts hexes moved before the skid begun, so they can't count a hex occupied by a DropShip, and since rules for colliding with a DropShip say that a skidding unit stops before entering a hex containing a DropShip, and stays there regardless of the collision outcome it is obvious that the hex containing the DropShip can't be counted when calculating skidding damage.

6. First sentence in the Accidental Falls From Above section. It makes no sense to say that a level is "greater than the maximum allowable level change". Change "whose level is lower and greater than the maximum allowable level change" to "whose level is lower by more then than maximum allowable level change". This may require a similar change in BMM as well if you made a change to Accidental Falls From Above paragraph on p. 70 BMM for some reason as a part of rewrite you mention in point 11.

Should I make separate threads and/or errata posts for topics discussed in points 8 and/or 9?

[Xotl]

4. Easy enough; done.

5. Done.

6. Done.

New threads for the remaining material please.

[Alfaryn]

Firstly, can I ask you to upload the current drafts please? The changes you mentioned in the last post don't appear in the documents under dropbox links you posted in this thread, and I want to make sure that these edits did not break something.


Re 4. Sorry, looks like I missed that at some point you changed the rules regarding collisions with other units to say that a skidding unit enters the hex with Other Unit(s) first, then resolves skidding damage (including for that hex), followed by resolving unintentional charge(s) to hit rolls and damage, and a displacement of charged unit (and i guess possibly any other units in that hex that may volatile stacking rules - for example if a 'Mech belonging to player A unintentionally charges a tank belonging to player B, and there is another 'Mech belonging to player B, the 'Mech belonging to player B would need to be displaced despite not being hit by a charge).

I was operating under assumption that the skidding unit stops one hex short of entering the hex with Other Units, resolves skid damage up to that point (that is without counting the hex with the Other units), resolves the charge(s), and if the charge hits and fails to destroy either of the units involved - both the skidding and the charged are displaced by one hex if possible (per general charge rules), at which point the problem would be if the skidding 'Mech suffers skidding damage for entering that last hex post-charge. The change I proposed in point 4 was to make it clear that it doesn't, because that last hex is entered under Location After Attack rules (p. 148 TW), not under skidding rules, but with your change it is clear that the charging 'Mech does suffer skidding damage for entering the hex containing the Other Unit(s), and happens before the collision is resolved.

The good thing about letting the skidding unit enter a hex with Other Units first, then resolve skid damage up to that point is that the change I proposed in point 4. doesn't matter - both sequences work, and produce the same result. There are however a downsides you may want to consider. What if the Other Units can't be displaced after the unintentional charge due to prohibited terrain? Does it mean that a skidding 'Mech returns to hex it came from, but somehow keeps skidding damage for entering a hex it ultimately did not ended up in? Another problem is that if a unit skids into a building hex containing another unit, there is a question whether to resolve collision with the unit or the building first. If a skidding unit stopped before entering a hex with Other Unit, resolved the skidding damage, then the charge against the other unit, and finally a post-charge displacement, the sequence would be obvious - first resolve a charge against units in a building, and then if a charging unit ends up being displaced into the building (or continuing to skid into the building if the charge missed or destroyed the target unit) - resolve damage for being displaced into post-charge or skidding into a building using rules on p. 151 TW or p. 62 TW as appropriate.


Finally as for the threads regarding the other material, I was thinking about making three threads about:
- Problems with the sideslipping rules,
- Thoughts about possible rewording and possibly slightly changing the rules regarding DFAs against submerged units (not just Naval Vessels) and landed Airspace units,
- Hull breaches checks for skidding damage if a skid ends in depth 1+ water (unless you want to discuss this one here?)

However I think that I will create these threads only after we finish with this thread. No point in discussing these issues when changes made here may influence what I may want to post in these new threads.

[Xotl]

Re 4. Sorry, looks like I missed that at some point you changed the rules regarding collisions with other units to say that a skidding unit enters the hex with Other Unit(s) first, then resolves skidding damage (including for that hex),

I didn't change it so much as spell it out, as the TW and BMM skidding examples both have that but it's not explicitly stated in the rules text, and I wanted that clear.  Part of the difficulty of these sections is how much of the actual process can only be gleaned through the examples.

If the ’Mech collided with the ProtoMech in Hex 2A, the
controlling player would first apply the damage (a 5-point and
4-point Damage Value groupings) from the fall and skid to the
hex occupied by the ProtoMech

("to the hex occupied by the ProtoMech" is a bit ambiguous, but as the mech fell in the hex immediately before it, the only way for it to apply damage via skidding is if it skid the one hex into the one containing the ProtoMech)

As the Phoenix Hawk weighs 45 tons, it suffers 5 points of
damage falling into Hex G, where it failed its Piloting Skill Roll (45
tons divided by 10 is 4.5, rounded up to 5) and 3 points of damage
for skidding into Hex 2A

What if the Other Units can't be displaced after the unintentional charge due to prohibited terrain? Does it mean that a skidding 'Mech returns to hex it came from, but somehow keeps skidding damage for entering a hex it ultimately did not ended up in? Another problem is that if a unit skids into a building hex containing another unit, there is a question whether to resolve collision with the unit or the building first. If a skidding unit stopped before entering a hex with Other Unit, resolved the skidding damage, then the charge against the other unit, and finally a post-charge displacement, the sequence would be obvious - first resolve a charge against units in a building, and then if a charging unit ends up being displaced into the building (or continuing to skid into the building if the charge missed or destroyed the target unit) - resolve damage for being displaced into post-charge or skidding into a building using rules on p. 151 TW or p. 62 TW as appropriate.

I think you're right.  That means adjusting the examples too...

It's probably worth adding text to resolve the case of colliding with building that also has a unit in it, if I can make it fit.  God I hate these rules.

Finally as for the threads regarding the other material, I was thinking about making three threads about:
- Problems with the sideslipping rules,
- Thoughts about possible rewording and possibly slightly changing the rules regarding DFAs against submerged units (not just Naval Vessels) and landed Airspace units,
- Hull breaches checks for skidding damage if a skid ends in depth 1+ water (unless you want to discuss this one here?)

However I think that I will create these threads only after we finish with this thread. No point in discussing these issues when changes made here may influence what I may want to post in these new threads.

That's fine: make the first two.  I think the third is already resolved.

[Alfaryn]

I think we are getting there. Just a few things, most of them minor:

1. In the general collision rules in both books:

For example, if a ’Mech falls and skids four hexes, but runs into a building hex in the second hex of its skid—which it destroys and so continues to skid
change to:
For example, if a ’Mech falls and skids four hexes, but runs into a building hex in the second hex of its skid—which it destroys and continues to skid

The fact that the 'Mech destroyed the building doesn't automatically mean that the skid will continue in this case. The 'Mech could fall into a basement or have its hexes left to skid reduced to zero if it the building was Medium or sturdier. This example doesn't need to discuss these mechanics as they are explained in the rules dealing with collisions with buildings specifically, but it shouldn't suggest that it is certain that the skid will continue.

2. I don't like how you use phrase "collision scenario" three times in general collision rules section. It feels almost like you introduce a new term "collision scenario" that is somehow different from just a "collision" (and the difference is not even clearly defined). To make it worse the phrase is never used outside of this one section. Maybe:

A collision scenario interrupts the normal skidding damage resolution process. Each collision scenario will tell you
change to:
A collision interrupts the normal skidding damage resolution process. Each collision scenario described below will tell you
or to:
A collision interrupts the normal skidding damage resolution process. Each collision scenario described no p. 71 will tell you

depending on whether Collisions With Stationary Objects begins on p. 70, or 71.

3. In TW you can save some space by doing the following in the DropShips paragraph:

Resolve a collision as if the DropShip were charged. However, calculate damage to the skidding unit using its own tonnage, rather than that of the DropShip’s.
change to:
Resolve a collision as if the DropShip were charged (see Charge Attacks, p. 148).

The rules on p. 148 already explain how to calculate damage to a unit that charged a DropShip. This space may come in handy in point 6. below.

4. "The charge is resolved immediately and, unlike standard charge attacks, can affect a unit that has not yet moved." In TW, Other Units section begs either for a reference to Avoiding a Collision section later on the same page, or for moving DropShip and Other Units sections between Water and Avoiding a Collision sections.

5. This is a big one. Basements rules on pp. 179 TW and 66 BMM lack a rule that explains what happens if a ground floor of a building with a basement a unit would fall into, and by doing so deals enough damage to the building to cause it to collapse. To keep the rules consistent with the sequence of events described in the current draft of collisions with Empty Buildings rules in BMM both Basements sections in TW and BMM should include a sentence explaining that any rolls in Basements Table and falls into basements are always resolved before building collapses. This way we not only solve the rules ambiguity that goes beyond crashes into building during skids (since this situation may also happen as a result of a regular move, displacement etc.), but also allow us to simplify how the rules explain interactions between skids and basements. Possibly to a point where we can squeeze that explanation to TW - see below.

6. In TW, Buildings section:

If the building hex is destroyed and the skidding unit still has hexes it is required to skid
change to:
If the building hex is destroyed, and the skidding unit did not fall into a basement (see Basements p. 179) and still has hexes it is required to skid

The idea behind this change is twofold - it reminds the reader to use Basements rules after skidding into a building without filling Skidding section with details that can't be fit there due to lack of space, and which Basement section explains anyway, while at the same time it covers the only case when a basement may cut a skid short. After all if a building hex a unit skid into doesn't collapse, the skid ends in that hex regardless of whether the unit falls into a basement or not.

7. You could probably do something similar to the trick in point 6. to save a lot of space in BMM, but if space isn't a problem, by all means leave the detailed explanations of interactions between skids and basements in the collisions section. It should save the readers a lot of page flipping and head scratching. Just make the following changes:

Check for a basement (see p. 66); if there is a basement, the fall occurs first, before a building collapse
change to:
Check for a basement (see p. 66); if there is a basement, the fall (if any) occurs before a building collapse

This covers both the fact that a unit may have a small basement which has no effect on 'Mechs and the fact that even if there is a basement big enough for the 'Mech to fall into, the fall may not occur because it does if building hex’s CF at the start of the current Movement Phase, not after the building suffered charge damage, was lower then the skidding 'Mech's tonnage.

If the building hex is not destroyed (or if there was a basement), the ’Mech’s skid ends in that building hex.
change to:
If the building hex is not destroyed or if the 'Mech fell into a basement, the ’Mech’s skid ends in that building hex.

As previously - even if there is a basement there is no guarantee that the 'Mech will fall into it.

If the building hex is destroyed and there was no basement,
change to:
If the building hex is destroyed and the 'Mech did not fall into a basement,

Same reason as before.

For example, if a ’Mech skid into a Medium Building hex, destroyed that building hex,
change to:
For example, if a ’Mech skid into a Medium Building hex with no basement, destroyed that building hex,

In my opinion this is the simplest, shortest way to fix that example.

[Xotl]

Changes made, except for the extra detail on #4 and the collision scenario wording.  I've actually deleted #4 because it's not a rule, just a "fun fact", and I need the space.  As for the latter, I'm fine with the term: all it is is a way of not saying "collision" full-stop, because potential collisions with units causes an interrupt even if you don't actually wind up colliding with anything.  No one is going to read it and think there's secret detail missing, and it doesn't appear after that para because we then move to the realm of the concrete (i.e. specific types of collisions) and so it doesn't need to appear after that para (though scenario occurs once).  But I tweaked the para a bit so it appears less in any case.

[Alfaryn]

Got a few more, unfortunately:

1. TW, general rules for collisions: "If at any time during a collision and the application of damage the skidding unit is destroyed, the skid ends immediately, with no further effects applied or resolved."

Not entirely sure what this sentence is supposed to mean. I guess that:
a. if a skidding 'Mech is destroyed by skid damage before resolving a crash, no crash or continuation of a skid is resolved.
b. if a skidding unit is destroyed during a crash, both damage and any post-damage effects (displacement, PSR to stay standing, collapse etc.) applied by the collision to the target should be resolved, but the skid does not continue even if the target of a charge is destroyed.

The problem is that the rule in TW does not imply a. at all, and is ambiguous about b., especially when it comes to post-damage effects.

Interestingly I don't see any such rule in BMM at all, and both books explain a. in the example texts on pp. 64 TW and 69 BMM, while the part about post-damage effects in b. isn't even explained in the general rules for charges on pp. 148 TW / 35 BMM (which is possibly something to fix there), while the part about not continuing the skid should be common sense to anyone who understands a.

So perhaps TW the best thing to do would be to scratch the entire sentence mentioned at the beginning of this point from TW, and depend on the example text and/or any clarifications you may want to add on pp. 148 TW / 35 BMM to explain what happens to a target of a charge during which the attacker gets destroyed?

If you want to make a. an b. clear in the skidding rules however (as opposed to just the examples on pp. 64 TW/69 BMM and the general charge rules on pp. 148 TW / 35 BMM), then perhaps you could also change the "[...] first resolve all damage to the skidding unit from its fall and the hexes it skid up to and including that point (if any). Only then is the collision scenario resolved. If a unit continues to skid after resolving it, the additional skidding damage is resolved afterwards." fragment in TW (and its counterpart in BMM) to something like "[...] first resolve all damage to the skidding unit from its fall and the hexes it skid up to and including that point (if any). Then, if the the unit is not destroyed, resolve the collision scenario. If the unit survives the collision, and continues to skid after resolving it, the additional skidding damage is resolved afterwards."

2. We may need a reminder in Occupied Buildings section in BMM about the fact that buildings protect partially protects units inside them from charge attacks per Attacking 'Mechs Within Buildings section on pp. 71-72 BMM. The rules proposed in TW simply say to use the rules for attacking Other Units first in this situation, and Other Units section simply refers the players to Charge Attacks section on p. 148 TW (which in turn mention Attacking Units Inside Buildings section on p. 171 TW), then we probably need no extra explanation in the skidding rules in TW, though it would be nice to have a reminder about p. 171 TW either in the last sentence of the Buildings section or in the Other Units section if you can squeeze it (possibly thanks to the extra space you can get if you follow my suggestion in 1.)

3. In both books change "four hexes" in the example text in the general rules for collisions (not in the Buildings/Empty Buildings sections) to something like "six hexes" - if a 'Mech makes a four-hex skid, and destroys into a building in the second hex, then it will not skid more than one hex afterwards (because even a Light building will reduce the number of hexes left to skid by one), and the example suggests that it could still skid additional hexes (plural).

4. In Occupied Buildings section in BMM: "If the ’Mech already in the building is displaced or destroyed as a result, the skidding ’Mech then moves into the building hex and a collision with the now-empty building is resolved as normal, after which its skid ends in that hex." Scratch "or destroyed" from this sentence - if the target 'Mech is destroyed, the skid continues as normal, so if the skidding 'Mech subsequently destroys the building hex as well, it may continue to skid past it.

[Xotl]

1. TW, general rules for collisions: "If at any time during a collision and the application of damage the skidding unit is destroyed, the skid ends immediately, with no further effects applied or resolved."

Not entirely sure what this sentence is supposed to mean.

I'm not sure how anyone could interpret it as anything other than A (plus displacement).  The moment a skidding unit is destroyed, the skid is over and you stop resolving anything to do with the process beyond the point of destruction.  No displacement, if any would normally be called for, would be the main thing.  Please understand that I don't want to re-edit the chapter in this thread.  I've added a version of the sentence to the BMM draft because it probably should be in there, since the core rules only cover destroyed units at the end of a phase, not mid-phase.

2. We may need a reminder in Occupied Buildings section in BMM about the fact that buildings protect partially protects units inside them from charge attacks per Attacking 'Mechs Within Buildings section on pp. 71-72 BMM.

I suppose.  May have to be cut later for space reasons.

3. In both books change "four hexes" in the example text in the general rules for collisions (not in the Buildings/Empty Buildings sections) to something like "six hexes" - if a 'Mech makes a four-hex skid, and destroys into a building in the second hex, then it will not skid more than one hex afterwards (because even a Light building will reduce the number of hexes left to skid by one), and the example suggests that it could still skid additional hexes (plural).

Sure.

4. In Occupied Buildings section in BMM: "If the ’Mech already in the building is displaced or destroyed as a result, the skidding ’Mech then moves into the building hex and a collision with the now-empty building is resolved as normal, after which its skid ends in that hex." Scratch "or destroyed" from this sentence - if the target 'Mech is destroyed, the skid continues as normal, so if the skidding 'Mech subsequently destroys the building hex as well, it may continue to skid past it.

Want to keep all scenarios that move the skidding mech into the building, but I've adjusted the text for accuracy.

[Alfaryn]

Quick note regarding 1.: I didn't mean either a. or b. I meant that IMO both a. and b. should be true. If destruction of a charging unit through damage it suffers during a collision with the target (as opposed to post-charge fall for example) prevents any subsequent effects to the attacked unit (such as displacement due to the charge and PSR to stay standing), then it looks like I misunderstood how charges are resolved (and not just unintentional ones). All the more reason to clarify it in the charge rules on pp. 148 TW / 35 BMM. Unless you only meant displacement of units other than the target of the charge (due to stacking rules violation for example)?

I will edit this post once I find the time to check the other changes. Should be within one or two days.

[Xotl]

Quick note regarding 1.: I didn't mean either a. or b. I meant that IMO both a. and b. should be true. If destruction of a charging unit through damage it suffers during a collision with the target (as opposed to post-charge fall for example) prevents any subsequent effects to the attacked unit (such as displacement due to the charge and PSR to stay standing), then it looks like I misunderstood how charges are resolved (and not just unintentional ones). All the more reason to clarify it in the charge rules on pp. 148 TW / 35 BMM. Unless you only meant displacement of units other than the target of the charge (due to stacking rules violation for example)?

The skidding note about destruction and possible follow-on displacement covers every possible means of damage, not just charges, but yes, if you're destroyed as part of a charge or a skid you wouldn't then advance into the target's hex or move the target, because you're dead (just like it says in the BMM with regards to charges that if the target is destroyed, it doesn't get displaced).  I can add a note on this for charges in both books if that's not clear (to be fair, TW has neither scenario covered), but while it doesn't say that about the attacker in the BMM, common sense plus the note there immediately following about the target not doing so makes it pretty intuitive, I think.  Assuming I'm not missing some other dimension at play here.

[Alfaryn]

If I interpret your answer correctly both Charge and DFA rules should:

A. say that if the attacker gets destroyed, the target is not displaced.
B. if either the attacker or the target  gets destroyed, say whether the surviving party should make a PSR to stay standing.

To me A. isn't intuitive, because even if the attacker is destroyed, the target was still hit by a multi-ton object moving at dozens of kilometer per hour, so I would expect some of that momentum to carry over to the target, especially since even a seemingly less violent Push Attack achieves the same effect.

The only thing that seems intuitive to me at this point (and pretty much explicit in BMM, though not in TW) is that even if the target is destroyed, the attacker should move into the target's hex.

[Xotl]

In BT it's the standard rule that your multi-ton machine vanishes from the face of the earth at the end of the portion of a 10-second turn in which you were destroyed, with no effects of any kind on the world after that, not even as wreckage.  This is only extending that standard ruling by a second or two before the end of the phase.  The BMM already makes this displacement principle explicit (Displacement, p. 55, under Destroyed Mechs), and there's a reference to the same idea in that book under Charges ("If the target ’Mech is not destroyed, it is displaced...") and DFAs ("If the DFA succeeds, the target (if not destroyed) is displaced...").  I don't think this is in TW under displacement because there's never enough room in TW to shoehorn in all the clarifications it needs, unfortunately, but I might be able to squeeze it in.

In any case, I've adjusted the wording on DFAs and charges in both books to better reflect this.  But it already worked this way.

As for PSRs, they're different.  They're a standard side effect of damage, and so aren't ignored.  The current wording of the collision section errata says to just ignore displacement effects upon destruction, not all effects.

[Alfaryn]

The way I read Destroyed 'Mechs paragraph on p. 55 BMM, it says that the unit that was destroyed is not displaced, but the issue I brought up isn't about that. It is about what happens to the other unit involved in the charge - the one that wasn't destroyed. Same for the other rules you quoted they say that the target gets displaced if it is not destroyed. I was asking if the target gets displaced if the attacker gets destroyed (and in case of intentional charges and DFAs if the attacker enters the target's hex if the target is destroyed).

The way I read the BMM rules after a successful DFA the attacker enters the target's hex even if the target is destroyed (as there is no exception in the location after attack rules on pp. 36 and 37 BMM for this move), and the target gets displaced even if the attacker is destroyed as long as the charge/DFA is successful and the target itself isn't destroyed (again - no exception in the rules for the case when attacker gets destroyed by it's own attack). It is only that sentence in skidding section that may suggest otherwise, and the obvious case when the above moves/displacements can't happen due to prohibited terrain covered in Prohibited Displacement rules on p. 55. Similar story in TW - the Charge and DFA rules on p. 148 and 150 TW don't say not to move/displace one unit involved in Charge/DFA if the other one is destroyed, the Unit Displacement rules say int to move either one if one of them would be displaced into a prohibited hex, and only that one pesky sentence in the skidding rules may be interpreted to mean that if the attacker is destroyed by a collision damage, the target would be displaced even though the collision happened.

There is also admittedly the rule about destroyed units/'Mechs on pp. 128 TW and 49 BMM which says that "Destroyed units are removed from the map in the end of the phase in which they were destroyed, and have no further effect on game play." but this one is even more ambiguous, since it doesn't even clarify if the units stop having any effect on gamely as soon as they are destroyed, or only after they are removed at the end of the current phase. Of course to fully realize the general concept that all weapons fire and physical attacks are simultaneous, destroyed units need to have effect on game play until the end of the phase they were destroyed in, but if we go with that, then the consequence would be that a 'Mech destroyed by a Charge needs to stay on board and affect the game play until the end of the phase (at least during physical attack phase, since I know you ruled in the past that damage in the movement phase is actually resolved as soon as it happens, not at the end of the phase). Which actually conflicts with the idea that a charged unit shouldn't be displaced if it was destroyed earlier in the phase by the way - shouldn't it have a chance to physically attack a unit that charged it, just because initiative order dictated that the charge happened first? All in all I think that the rules on pp. 128 TW and 49 BMM aren't very useful to resolve my issue with movement/displacement of units that survived a Charge or DFA that destroyed the other unit involved, and if anything - further complicate the picture by possibly conflicting with Charge/DFA rules in BMM.

By the way, regarding Destroying a Unit rules on p. 128 TW the sentence "If tracking damage for salvage purposes/campaign play, resolve an automatic fall if the ’Mech was standing at the start of the phase it was destroyed in; a MechWarrior who survives in such a scenario suffers automatic falling damage as well." should probably be turned into its own paragraph and/or moved above the Forced Withdrawal section, because it seems applicable regardless of whether the destroyed unit operated under Forced Withdrawal rules or not. Also the "if the ’Mech was standing at the start of the phase it was destroyed in" bit needs to be changed to something like "if the ’Mech was standing when it was destroyed", because if a 'Mech got up during a phase during which it was destroyed without falling back first (possible during a Movement Phase), you obviously should resolve a post-destruction fall, and if a 'Mech fell before it was destroyed (or was destroyed as a result of a fall (possible in multiple phases), you obviously shouldn't.

Other than that, I've found just one more problem with the current BMM draft. In Dodging a Collision section the rules say to make a PSR to dodge a skid "Before the skidding ’Mech enters the target’s hex". Considering that in current draft the skidding unit enters the target's hex only after the charge damage is resolved this rule needs to change, preferably in a way that explains if the collision still happens in case the dodging unit successfully makes a PSR to dodge, but then for whatever reason fails to leave it's hex. Similar change needs to be made in Avoiding a Collision section on p. 63 TW.

[Xotl]

By the way, regarding Destroying a Unit rules on p. 128 TW the sentence "If tracking damage for salvage purposes/campaign play, resolve an automatic fall if the ’Mech was standing at the start of the phase it was destroyed in; a MechWarrior who survives in such a scenario suffers automatic falling damage as well." should probably be turned into its own paragraph and/or moved above the Forced Withdrawal section

Was already noted for the next printing.

Other than that, I've found just one more problem with the current BMM draft. In Dodging a Collision section the rules say to make a PSR to dodge a skid "Before the skidding ’Mech enters the target’s hex". Considering that in current draft the skidding unit enters the target's hex only after the charge damage is resolved this rule needs to change, preferably in a way that explains if the collision still happens in case the dodging unit successfully makes a PSR to dodge, but then for whatever reason fails to leave it's hex. Similar change needs to be made in Avoiding a Collision section on p. 63 TW.

I can just delete the timing note, saving the room: when it occurs is already clear (after a successful charge roll but before damage is resolved).

I'm wrapping this thread up: not to disparage your efforts, but I've already spent a week of my BT time on a ruleset maybe a dozen people use, and I have other things that need tending to.  Thank you for your time: it's in far better shape than it was at the start, both in terms of legibility and actual playability (insofar as these rules are playable at all).

[Alfaryn]

No problem, I do realize that I took a lot of your time here, though I would say that more than just a few people use this ruleset. It is implemented in MegaMek after all... And besides - if the ruleset is better in terms of legibility and playability, then perhaps more people will start using it in actual tabletop play, especially with a city-themed MapPack appearing in the Mercenaries Kickstarter.

Seriously though, thank you for your patience and effort. Expect me to post the other threads I promised in this one soon. Don't feel pressured to deal with them quickly though. I do realize that after this thread you may want a break from this corner of the ruleset (if not from Battletech rules questions in general), I just want to put my questions out there before I forget the specifics of what I wanted to suggest and ask about.

As for the note you are about to delete - keep in mind that the rules still don't say if the collision happens if the target of an unintentional charge makes a PSR to dodge, but fails to leave the hex during the movement that roll grants it. Perhaps it is something to add at a later date?

[Xotl]

As much as I wanted to put this to bed, when I went to update the examples to match I found additional issues, mostly regarding how the rules handle automatic dodges and skid interruption (something again not really called out in the rules text but clear in the examples).  As such, I've made further modifications, if you want to review them.  The bottom of the TW page also has the example text portions that are being updated.

[Alfaryn]

"Each time a skid is interrupted afterwards with another collision scenario, apply all skidding damage to that point that has not yet been resolved." in TW and its counterpart in BMM while correct, should in my opinion be obvious, and as such should be the first sentence to cut if space is a problem.

Other than that and my concerns about resolving location after a unit surviving Charge or DFA attacks if the other unit involved was destroyed (and the physical attacks of units that were destroyed by a Charge or DFA before they had a chance to attack themselves), which I already expressed above and which should in my opinion be addressed in general rules for Physical Attacks and Displacement before we deal with how they interact with skids, I can see no more problems with the BMM draft. I wonder, however, about that new rule that says to resolve that last hex of skid damage after a successful unintentional charge. What prompted the change? Details of these long example texts on pp. 64-66 TW and 68-70 BMM?

By the way, should I make a separate thread for these problems with unit destruction during a Charge or DFA?


TW is a different matter. Generally I think that moving Infantry and ProtoMechs sections from p. 64 crates more problems than it solves:
1. "Other Units" in the last sentence of Buildings section would need to be changed to "Other Units, Infantry, and ProtoMechs",
2. "[...]does not use its movement for the turn, and is not required to make any kind of roll." in Infantry section is confusing, because it appears before the general rules for avoiding collisions and would thus require yet another reference,
3. "[...]charge damage dealt to them is as normal[...]" in ProtoMechs section may be confusing because not only the "normal" way of resolving collision damage with Other Units is not yet explained, there are plenty of other methods of resolving collision damage with various obstacles in the skidding rules, and it is not immediately clear if the reference to Other Units applies to both damage and halting a skid, or only to the latter.
4. Both Infantry and ProtoMechs sections fail to avoid making references to Other Units section. That makes three explicit references to that section in four sections directly preceding it - both waste of space and unnecessary hurdle for the reader to deal with in my opinion.

I think it would be better to change the beginning of Other Units section to something like:

"If the unit in a hex in the path of a skid is an Infantry or a ProtoMech unit that has not yet moved, they may dodge a skidding unit automatically without interrupting the skid (see ProtoMechs and Infantry, p. 64). Otherwise the skidding unit stops in the hex immediately prior to it,[...]" and from that point the rest of the section remains unchanged except "[...]use the ’Mech Hit Location Table." would be changed to "[...]use the ’Mech Hit Location Table. Infantry units take damage equal to the skidding unit’s tonnage divided by 5 instead of standard Charge damage." and "After the crash is resolved, the skid continues if the target unit was destroyed." would be changed to "After the crash is resolved, the skid continues if the target unit was an Infantry unit or was destroyed."

and to move the Infantry and ProtoMechs-specific rules on dodging attacks back to p. 64, changing their text to something like:

"Infantry and ProtoMechs: Infantry and ProtoMech units that have not yet moved can automatically dodge a skidding unit without interrupting the skid; they stay in the same hex without using their movement for the turn or making any roll. If remaining in the hex would violate the stacking rules or the Infantry or ProtoMech unit has already moved this turn, however, then it cannot dodge, and the skidding unit may strike it as described under Other Units on p. 63."

Aside from hopefully solving the problems mentioned above, I think that it makes sense to keep specifics of Infantry and ProtoMechs rules regarding avoiding collisions right below Avoiding a Collision section, and Infantry-specific rules not dealing with avoiding collision (the way damage taken by them is calculated, and the fact that colliding with them does not interrupt skids) in the Other Units section. Also note that the first part of the proposed Infantry and ProtoMechs section text is almost the same as the proposed first sentence of the Other Units section. Perhaps there is a way to shorten one of these sentences in a way that doesn't make it too difficult to understand?

If you disagree with moving the rules on automatic collision avoidance by Infantry and ProtoMechs back to p. 64, then perhaps another way to at least partially deal with the issues I brought up (in particular 3. and to some extent 4.) would be to put Infantry and ProtoMechs as described above right above Other Unit section (and change "[...]under Other Units on p. 63" at the end of it to "[...]under Other Units, below", or just "[...]below"), and change the beginning of Other Units section to "If the unit in a hex in the path of a skid is not a DropShip or an Infantry or ProtoMech unit that automatically dodged a skidding unit, the skidding unit stops in the hex immediately prior to it,[...]" and keeping the rest of the Other Units section as described above - with Infantry-specific rules not related to automatic dodging scattered throughout it.

I think you could also consider stating explicitly in the Infantry and ProtoMechs section if a unit that can't avoid a collision automatically due to stacking limits violation, can still do it using the general rules in the Avoiding a Collision section. I assume that they can't, since neither ProtoMechs nor Infantry have Piloting skills, and thus can't make PSRs? If this is not the case, then "the Infantry or ProtoMech unit has already moved this turn, however, then it cannot dodge" in proposed Infantry or ProtoMech section text above should be changed to "the Infantry or ProtoMech unit has already moved this turn, however, then it cannot automatically dodge", and the rules should say what to do instead of the PSR required by general rules regarding avoiding collisions.

By the way, I'm unsure if it would be a good idea to delete Large Support Vehicles paragraph on p. 64, and just change "If the charge hits, the target may still be able to dodge[...]" in the Other Units section to "If the charge hits, and the target is not a Large Support Vehicle, it may still be able to dodge[...]" as well as "A unit that has not yet moved during the current Movement Phase can attempt to dodge a skidding unit[...]" at the beginning of Avoiding a Collision section to "Any unit other than a Large Support Vehicle or a DropShip that has not yet moved during the current Movement Phase can attempt to dodge a skidding unit[...]". I think that both leaving and deleting the section has various pros and cons, though I guess that at this point the preferred solution could be simply the one that takes up less space in the book.

Finally, a question that I posted earlier today in the new thread about sideslips, but which you may want to address in the Other Units section, especially if the answer isn't as straightforward as I suggest in the question:

How do the rules on Attacks Against Conventional Infantry (pp. 215-216) interact with unintentional charges against infantry? Do you take "the skidding unit’s tonnage divided by 5" (p. 64), then divide it by 10, rounding up (Non-Infantry Weapon Damage Against Infantry Table, p. 216), and double it again in case of mechanized infantry to determine the number of troopers eliminated (p. 215)?

As for the example text at the end of the TW draft, I don't see any problems with it.

[Xotl]

I wonder, however, about that new rule that says to resolve that last hex of skid damage after a successful unintentional charge. What prompted the change? Details of these long example texts on pp. 64-66 TW and 68-70 BMM?

Exactly: the examples are quite clear on that point, and I only want to outright change existing rules (as opposed to plugging gaps) if it becomes necessary to fix something unworkable, like the displacement timing issue you pointed out earlier.

By the way, should I make a separate thread for these problems with unit destruction during a Charge or DFA?

No, thank you.

TW is a different matter. Generally I think that moving Infantry and ProtoMechs sections from p. 64 crates more problems than it solves:

Upon further review I agree, and have remodelled the section largely according to your suggestions.

Finally, a question that I posted earlier today in the new thread about sideslips, but which you may want to address in the Other Units section, especially if the answer isn't as straightforward as I suggest in the question:

You'd follow the rules as you intuited.  I think that's clear enough via the text as-is that I don't want to add more text to deal with it.

Once again, thanks for the review.

[Alfaryn]

I don't have time to review the updated drafts right now, I will do it later. However I've just realized that there is another rules interaction that the skidding rules need to address - unintentionally charging units within buildings, which could interact with either Infantry Inside Buildings rules on p. 172, or Combat Within Buildings on p. 175.


Edit: I've read the newest TW draft. Here are the issues I've spotted:

1. Accidental Falls From Above paragraph - considering that it was moved out of the collisions subsection, it probably more than ever needs a clarification that initial fall and skidding damage should be resolved before the accidental fall from above is. Maybe something like "[...] but resolves any prior fall and skid damage first, and then experiences an accidental fall from above (see p. 152)." at the end of the first sentence would be sufficient?

2. The last paragraph of Buildings subsection (or possibly the beginning of Other Units subsection) should probably remind the players that if a skidding unit would enter a building hex, it doesn't unintentionally charge any infantry units in that hex as described in Other Units section, but instead automatically deals damage to the infantry units based on the charge damage dealt to building itself (per Infantry Inside Buildings p. 172).

Note that while technically the Infantry Inside Buildings would apply only to attacks from outside of the building, but it is impossible to skid more than one hex inside a building, without causing prior hexes to collapse and a skid can't start inside a building (at least under TW rules), so if a Rubble hex left by a collapsing building hex is considered "outside" (and I think it should), there is no need to make this distinction in the draft.

3. Considering that Large Support Vehicles rise 2 levels above the ground (see Levels and Height, p. 99), shouldn't charge damage dealt Large Support Vehicles to 'Mechs be applied using regular ’Mech Hit Location Table even if the 'Mech is standing? If so, it would affect both Other Units subsection in the draft and the Vehicles paragraph of the Damage subsection on p. 148.

4. "[...]the skidding unit takes an additional hex of skidding damage." in the last paragraph of Other Units subsection should probably be edited to let the player know that the damage only happens if the skidding unit actually enter the target's hex, which may not happen if prohibited terrain prevents post-charge displacements. Probably saying something like "[...]the skidding unit then takes skidding damage for entering the target's hex." would be sufficient.

5. Prohibited Terrain paragraph should probably be edited so that there is no doubt whether a unit that would skid through a hex with prohibited terrain stops there or skids through it, but becomes immobile, or becomes immobile only if the skid "naturally" ends in a Prohibited terrain.


As for BMM, I've skimmed through it, and noticed only one small change in the draft compared to the previous version (simplifying damage direction determination in the general Collision rules), which works fine in BMM as far as I can tell, so unless I've missed any other changes, the draft should be fine.


Edit 2: Regarding the changes in TW draft that appeared after my previous edit to this post:
- I assume, that the change I suggested in point 3. above won't be implemented?
- Re. point 1. telling the player to resolve initial fall, skidding damage and accidental fall from above together (as is in the current draft) is problematic, because the skidding rules say to determine the direction of incoming damage based on the direction of the initial fall, while the rules for Accidental Falls from Above on p. 152 say that the falling unit takes "standard damage from falling" if it misses all units in the hex it accidentally fell into (which seems to suggest that the fall and damage direction would be randomized independently from the initial fall direction), and, perhaps more importantly, that if the falling 'Mech does hit a target in the hex it fell into, it takes standard falling damage to its back. In other words if damage from initial fall, skidding damage and accidental fall from above, the rules conflict about which direction it is coming from, and as long as the conflict is there, these kinds of damage can't be resolved together.


As a side note it is not entirely clear how to resolve falling damage to a unit other than a 'Mech if accidentally falls from above, hits a unit in a hex it fell to. Should apply the falling damage as if it came from its rear, or randomize it with fall direction as normal? In fact Vehicles seem to lack any rules about determining fall damage direction and facing after fall other than the case of VTOL rotor destruction (which destroys the vehicle) and falls into basements (which say that the facing after fall remains unchanged, and in case of Vehicles damage direction is either front or rear depending on the direction of Vehicle movement before it entered the building hex - completely ignoring the fact that the vehicle may fall into a basement as a result of a "sideways" skid or sideslip, or due to another unit entering the building hex).

In other words we probably need a clarification for post-fall direction and damage resolution for non-'Mech units not only in Accidental Falls from Above section, but also in Basements section on p. 179, because the current rules don't seem cover all possible circumstances of ProtoMech and Vehicles falling into basements. Perhaps the best way would be to just have the Vehicles roll in Facing After Fall Table (p. 68) to determine damage direction if they accidentally fall fall into a basement as a result of action other than their own movement (except a skid in which I would determine the direction as in case of a collision - based on the direction of a skid)? In case of Vehicles accidentally falling from above during a skid or sideslip (p. 67-68) I wouldn't use the table to determine incoming fall damage direction at all, and instead determined it as if the Vehicle crashed into the hex it fall into (at least if the Vehicle did not hit any other unit while falling - the rules in Falling Unit Hits Target subsection on p. 152 should clarify if "Determine damage to the falling ’Mech as normal for a fall, with the ’Mech landing on its back" sentence in that subsection should be extended to falling Vehicles, or only applies to 'Mechs - I know the sentence says "'Mechs", but many rules in this chapter that refer to 'Mehcs in their text apply to other units after all, and in this case it is not obvious if the rule in question does).

As for the direction after a fall (both in case of accidental falls from above and falls into basements) I would determine facing of 'Mehcs and ProteMechs as normal (this would be a change for ProtoMechs falling into basements by the way), but in case of Vehicles I would leave it unchanged (i. e. same as before the fall) - falling vehicles tend to keep their direction after all but the longest falls from cliffs, etc. (that is - their front keeps pointing in more or less the same direction even after they roll on their roofs - a possibility that BT rules don't cover anyway). This is something that the rules regarding falls of Vehicles to basements already say to do anyway - I would just make it work this way for accidental falls from above. Of course if you think that in any of these cases the facing of vehicles needs to be randomized, then it should also be reflected in fall damage direction rules I suggested in the paragraph above. And if you decide to leave the ProtoMech facing after fall into basement rules unchanged, then I would suggest to implement the same rule regarding ProtoMech facing after falls from above.

[Xotl]

Edit 2: Regarding the changes in TW draft that appeared after my previous edit to this post:
- I assume, that the change I suggested in point 3. above won't be implemented?

No.  Not adding more exceptions and text here.

- Re. point 1. telling the player to resolve initial fall, skidding damage and accidental fall from above together (as is in the current draft) is problematic

Yeah, another case of the examples being crystal clear on how things are supposed to end up, but the supporting rules not detailing how to get there.  I've made adjustments to resolve this as a generic fall or as a collision scenario, as appropriate.

As a side note it is not entirely clear how to resolve falling damage to a unit other than a 'Mech if accidentally falls from above, hits a unit in a hex it fell to. Should apply the falling damage as if it came from its rear, or randomize it with fall direction as normal?

For the most part, just replace "Mech" with "unit" in that section (which is strange as TW is normally quite careful at making things suitably generic).

In other words we probably need a clarification for post-fall direction and damage resolution for non-'Mech units not only in Accidental Falls from Above section, but also in Basements section on p. 179,

I'm not going to deal with basements at this time.  It's just too much further work.

The draft size on TW has been expanded to cover even more of the skidding section, but for the most part there's few rules changes in the earliest stuff: it's mostly just cuts to allow other stuff later to fit, as the section is bursting at the seams.

[Alfaryn]

Once again, I don't have time to do a full review right now. I should be able to get around to it tomorrow. However even skimming a beginning of the TW draft revealed a few issues:
- Water paragraph mentions sideslipping before it is established in Ground Vehicles (Except Hover Vehicle) subsection what sideslipping is, and how it differs from skidding. You may consider putting a reference to either Ground Vehicles (Except Hover Vehicle) subsection or Sideslipping section in the Water paragraph.
- Shouldn't Ground Vehicles (Except Hover Vehicle) subsection be named Ground Vehicles (Except Hover Vehicles)?
- Skidding in Combat subsection says that "A skidding ground unit applies a +1 to-hit modifier to all weapon and physical attacks during the turn it skids." Examples on pp. 64-66 make it clear that this modifier doesn't apply to to-hit rolls for unintentional charges made by the skidding unit, but I think the rules should also mention it.


Xotl: Updated.


Issues with current TW draft spotted during a full read-through:

1. Terrain subsection - you can delete "(unless the hex is prohibited terrain; see p. 63).", since the last paragraph of that subsection includes this information.

2. Water paragraph - "If a hover vehicle suffered critical damage during a sideslipping". Considering that I'm not an English native speaker, I feel silly asking this question to someone who is, and probably read this fragment a couple times while working on this draft, but shouldn't it be "If a hover vehicle suffered critical damage during a sideslip"?

3. Skidding in Combat subsection - "A skidding ground unit applies a +1 to-hit modifier to its weapon and physical attacks during the turn it skids (except unintentional charges)." I'm not sure if that modifier should apply to accidental falls from above, but considering that it is supposed to represent pilot's imperfect control over a skidding unit, and all accidental falls from above (regardless of whether they happened as a result of skid or not) are obviously a situation in which the pilot has pretty much no control over his unit's movement, I suspect the mod shouldn't apply. If so, change the sentence to "A skidding ground unit applies a +1 to-hit modifier to its weapon and physical attacks during the turn it skids (except unintentional ones)."

4. Attack Modifiers Table pp. 117, 307, Skidding line - consider adding a note that the mod does not apply to unintentional charges or attacks as appropriate (see previous point).

5. Physical Modifiers Table pp. 144, 308, Asterisk (*) footnote - Is it possible to squeeze in an information that this mod does not apply to unintentional charges? I assume not, since it did not make it there when you resolved the same problem in BMM, but I thought I would ask in case you simply forgot to do it in TW.

6. Avoiding a Collision subsection - "Once the skidding unit’s movement is completely resolved, immediately adjust for the number of units shifted per side (see Unequal Numbers of Units, p. 39)." You can probably delete this sentence. It has no counterpart in BMM, and if you decided to keep it, you would probably also need to add similar ones to rules that describe a situation where a unit which has not moved is destroyed by an unintentional charge, accidental fall from above, a fall due to domino effect etc. I see no reason to adjust the number of moves earlier than just prior to a pair of movement or attack declarations the rules on p. 39 talk about anyway.

As for the BMM draft, I see no problems with it, though I suspect that points 1. - 4. may apply to BMM as well - just outside of the text covered by the draft.


Final edit (hopefully): Looks like there are no more issues with the drafts that I can see right now.

I may give them one last read-through in a few weeks or months once I get some distance from what we've done here, and a fresh perspective that will hopefully come with it. I'll also try to remember to check if all corrections outside of the scope of the drafts that came up in this thread make it into the next official errata document. Other than that I'm done with this thread.

Once again thank you Xotl for all your patience and work here, and sorry for all my mistakes and other failings here - from my general problems with writing correctly (not to mention concisely) in English, to occasional inability to read the rules, including that thing in point 3. of this post. It was only today that I realized that since to-hit rolls for accidental falls from above are modified only by target movement and terrain, the change I suggested in that point wasn't needed.


Xotl: Turns out reprints are coming up as of now, so I'll have to close this out for good.  Thanks again: this was very timely!

[Alfaryn]

Sorry for double posting, but considering the reprints are coming, I wanted to make sure Xotl sees this before submitting the final text for the upcoming TW and BMM printings if possible.

Currently it is unclear if the hexes a unit skidded, sideslipped and or was displaced during a turn should be counted towards it's target movement modifier. It could be clarified in Skidding in Combat subsection (p. 62 TW) and Combat Effects paragraph (p. 68 BMM), but considering that the problem involves not only skids and sideslips, but also displacements for other reasons, I think it would be better to do it in Target Movement and Target Movement Modifier subsections (pp. 107 TW and 25 BMM respectively).

Edit: Turns out that TW rules already say that hexes sideslipped count towards TMM (at the end of the fourth paragraph on p. 67). I still can's see any such rule for skids, displacements etc. though...