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Sorry, I was out of town for a few days, and had no time to figure out the answer on this one.

The presets you compare with were not automated through the PTA, so there is no reason why these should behave the same.

Are you sure the game ends when the King moves out of check? Normally an illegal move should not terminate the game; it should just be refused (in this case with the message you quote), and then through using the browser 'back' button you should be able to retry another move. This is also what happens if you insist moving a piece to a non-highlighted destination.

If this is the case the only thing that isn't working exactly as it should is the highlighting: the King jumps get highlighted even if they are forbidden because of check. But there is no way to exploit this; in the end legality is enforced by refusing the move.

The way the PTA-generated GAME code enforces 'not out of check' rules is by having the potentially forbidden moves generate e.p. rights on the square of origin. Using such a move then would allow the opponent to capture the moved piece (i.e. the King) en passant, making the move illegal.

Unfortunately the 'accelerated check test' used for determining the legality of the moves to highlight (in order to prevent this from becoming excruciatingly slow for large games) doesn't detect this: it generates all opponent moves from the current position to mark squares that are under attack on the board. And then only rejects King moves that go to such an attacked square. And in this case the problem is not that the destination is attacked, but that the origin is attacked.

I suppose I could solve this in the accelerated check test by suppressing the virginity of a King that is in check during the generation of the highlights.

[Edit] I now changed the move generator to suppress initial moves of a piece that should not move out of check, when it is in check during the accelerated check test. Please test if this solves the problem.