nabla: as soon as your opponent makes his 1st move

nabla: You only need to alter the rules to the extent of creating the new game, superfluous amendments don’t add anything except the ambiguity that you seek to avoid. You couldn’t pay three check chess without changing the definition of how the game ends. There is no need to do so in loop chess though. The only clarification of the rules that is needed in ice age chess is the assessment of checkmate occurs at the end of move 40 or the start of move 41. There is no need to refine checkmate in this game.

Justaminute / Nabla: I believe that in Atomic chess you should be considered to be in check if a move of your opponents could blow up the king.... i think that is a mistake in the implementation... however it doesn't really matter or change the game too much.

In this case you're asking the wrong question. Checkmate occurs at the end of move 40 - However - the definition of checkmate is that the king cannot move out of check on his next move. Since the next move is move 41, the ice age event intervenes and must be taken into account...

I don't see how the interpretation could possibly be any other way unless it is explicit in the rules (which it isn't).

You can argue that it is a lop-sided game as a result if you like, but I don't think you can argue the interpretation;.

grenv: I think that the crux of our disagreement is this: when does a test for mate occur?  I contend that a move that would--in a given position--suffice to produce mate on any move numbered 21 through 39, would also produce mate on move 40.

I think the move 40 sequence is: (1) black plays a move, (2) one tests for mate, (3) if not mate, an ice age occurs, (4) one tests for frozen king(s).
I think your move 40 sequence is: (1) black plays a move, (2) an ice age occurs, (3) one tests for mate or frozen kings.

In your sequence only, it has become simultaneously possible for the white king to be mated and for the black king to be frozen--yet another situation not mentioned in the game description at chessvariants.org

wetware:
point 1... Move 40 is defined as being different in the rules... assuming that it should behave the same is plainly wrong.

point 2... Actually my sequence is the same as yours, I just have a different definition of checkmate... my definition is;
"if the white king is in check and cannot legally move out of check on his next move, then he is checkmated."

Your definition appears to be:
"if the white king is in check and could not legally move out of check next move in an identical situation in a different variant, then he is checkmated"

I like my definition better.

grenv:
"point 1... Move 40 is defined as being different in the rules... assuming that it should behave the same is plainly wrong."

Plainly (please read for yourself), there is no such definition of moves 20, 40, etc., being inherently "different".  But by rule something special does happen after each of those moves (assuming, of course, that the game does not actually end on any of those moves.)  I do hope you agree that a game can be ended by a black move 20, 40, etc.

"point 2... Actually my sequence is the same as yours, I just have a different definition of checkmate... my definition is;
"if the white king is in check and cannot legally move out of check on his next move, then he is checkmated." "

Checkmate ends a game.  There is no "next move".  Plainly, the mating move is the last move of a game.  So any definition that demands a reference to a "next move" must be doing so in a hypothetical way, as it refers to something counterfactual--it will not occur.  In my opinion, it's better to avoid that in a definition if that can reasonably be done.

Your definition appears to be:
"if
the white king is in check and could not legally move out of check next
move in an identical situation in a different variant, then he is
checkmated"

Plainly not.  My test for mate after Black's move 40 would be the same as the test applied after moves 21 through 39.  I think that would be the same evaluation applied in conventional chess.

And please tell me when you perform the test for mate: before the ice age?

wetware:

from thefreedictionary.com - but all definitions are essentially the same

check·mate (chkmt)
tr.v. check·mat·ed, check·mat·ing, check·mates
1. To attack (a chess opponent's king) in such a manner that no escape or defense is possible, thus ending the game.

After move 40 an escape *is* possible if the ice age event would cause the king to avoid capture.

Honestly, you people think this is opinion - it isn't... we are trying to interpret the rules as written. I believe my interpretation is the only possible interpretation.

*Opinion* might be that this rule isn't a good rule and should be rewritten.

grenv: Oh, and one last comment... whether you know it or not, you are taking the possible next move into account when assessing if it's a checkmate.... otherwise it makes no sense. If you don't see that then it's no wonder you don't see my larger point.

You might google parallel lines in non-Euclidian geometry if you want some ideas on how interpretation of definitions should not be swayed by your experience and pre-conceived notions.

grenv: I'd still like to hear your answer to this question: to which position do you apply the test for mate?  Is it (my contention) to the position at the end of move 40--before the ice age?  Or is it to the position after the ice age adjustments--with White about to make move 41?  It's a clear question, I think...and crucial.

If you claim that the ice age adjustments between moves 40 and 41 must be taken into account, note those same ice age adjustments could iinclude a black king's being frozen to death at the same time that white's king is mated.  Or you'd be stuck claiming that you only consider the ice age consequences for some purposes that you choose, while ignoring other consequences of that identical event.

wetware: The *test* for mate is after the 40th move.... but the *definition* of mate relies on knowledge of what the king *could* do next move.... therefore checkmating takes precedence in this case - it happens one move before the other event.

nabla: In conventional chess, can I be checked (or even mated) by a pinned piece?  Or is that another optical illusion?