This problem seems to be a bit more general than I thought. Here is a different case that seems to break down:
I can find no way of choosing whether I want to add a piece to the top of a stack or remove one. I hope there is a systematic way of tackling these issues.
(Edit: I forgot to add "count:1" to (move Remove), but it doesn't change the problem.)
Code:
(or
(move Add (to (sites Board)) stack:true)
(move Remove (sites Board))
)
(Edit: I forgot to add "count:1" to (move Remove), but it doesn't change the problem.)