[Retros] Two-pawns chess

[Joost de Heer]

On 15-9-2012 5:23, werner wrote:

> I don't see where the discussion about the 'checks' comes from. I think

> Eric was clear about the rules. I quote: 'orthodox rules + just one

> unorthodox rule: if your opponent captures a second pawn (of yours), you

> have lost the game.' Obviously there is no mention of so called

> 'checks', so 1.e4,d5 2.e5 seems perfectly legal to me.


The legality of the proofgame '1. e4 d5 2. e5' was for '1-pawn capture 
chess'. Because the rule says that you win if you capture the N-th pawn 
(and not if you threaten to capture the pawn and the opponent can't do 
anything about it), the question remains: Is capturing (N-1) pawns and 
then threaten to capture the N-th pawn check? In other words: In 1-pawn 
capture chess, is 1. e4 d5 an illegal move? Black makes it possible for 
white to capture the Nth (in this case first) pawn. The rules don't 
stipulate that capturing the N-th pawn if possible is obligatory. For 
most chess compositions this difference is irrelevant, but for 
proofgames this is very relevant:

r1bqkbsr/pppppp1p/2s5/8/6p1/1S1P4/PPP1PPPP/R1BQKBSR
1-pawn capture chess, proofgame in 3.0 moves. How many solutions?

A similar discussion arose when I composed an extinction chess game 
where the move order was defined by such 'checks':

1rb1k1r1/p2psp1p/2s5/1qp1p3/8/8/1PPPPbPP/RSBQKBSR
SPG 10.0 Extinction chess

1. f4 e5 2. f5 Bc5 3. f6 Se7 4. fg7 Bf2+ 5. g8=K! c5 6. a4 Qb6 7. a5+ 
Qb5 8. a6 Sc6 9. ab7 Rg8+ 10. b8=K! Rb8+

All these checks are not checks in the original definition of Extinction 
chess, and therefore, when using the original definition of Extinction 
chess, this is horribly dualistic.

Joost