Why is this move illegal? Is it a bug?
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I'm trying to capture the bishop with my pawn g2->h3 and it only lets me move it to g3 or g4. Why?
Well, as you move your pawn to g3, then your king is wide open for the queen in g6 to attack it. That's why you can't move your pawn.
So it was right there the whole time! Thanks 
This is an example of an (absolute) pin.
j
