Illegal Position Contest!
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Typewriter44
Mar 23, 2017
0
#361
Mar 23, 2017
0
#362
I believe its Illegal, If so proving it would not be a difficult task
RelaxPanos wrote:
legal
Travkusken wrote:
Legal in Chess960 lol
Adihere skrev:
Travkusken wrote:
Legal in Chess960 lol
No, it's not legal in chess 960. In chess 960 the rooks are not allowed to be placed on the same side of the king and there is no way the rook could have been moved to that square because of the bishop.
uuuuuuuu47 wrote:
cobra91 wrote:
All but two of the positions I posted have already been proven as illegal, leaving just these:
it's illegal because the pawns that would promote wouldn't be able to get past each other without capturing each other
Have a look at the demonstration below. 
SHRDLU wrote:
cobra91: The first one must be illegal. Both white and black need at least 7 pawns to get 2 extra rooks, 2 extra knights and 3 extra light squared bishops. 2+2+3=7. Assuming that 1 pawn walked straight to the other side through a pawnhole on the d- or e-file in the enemy's camp, than the second has to capture one piece to go through that same hole, the third has to capture 2 pieces, etc, which gives 3+2+1+0 (the pawn walking straight through the hole in the opponents camp)+0 (the pawn captured by the opponent to make a hole)+1+2+3=12 captured pieces. The only pieces that could have been captured, at best, are: 1 black-squared bishop, 1 queen and 1 pawn = 3 pieces. I say "at best" which is the case when both parties still have the original 2 knights, 2 rooks and 1 light-squared bishop. Since 12 must have been captured and only 3 could have been captured leaves this position illegal. Ammiright?
You guys are both using the same argument to prove illegality, but it doesn't quite work:
Typewriter44 wrote:
I believe its Illegal, If so proving it would not be a difficult task
It's legal.
Mar 24, 2017
0
#371
cobra91 wrote:
Concrete proof is elusive, but I think the position below is illegal. If anyone believes they can demonstrate otherwise, please let me know!
@g6 could only get there from this position:
But that position is also Illegal:
If it was like this, it would be legal, I will post more proof tomorrow
Giocio Piano REV.
Mar 25, 2017
0
#376
Because of the opposite colored bishops. (I bet you thought you were soooo smart).
SHRDLU wrote:
I stand corrected. Great work!
Sorry for accidentally quoting the wrong part of your earlier comment (post #359). 
I've edited post #380 so that the quote makes much more sense in the given context.
Anyway... what do you think about the diagram from post #239 (or equivalently, the 1st diagram from post #358)? Is the position legal, or isn't it?