Play chess against a computer!

Instructions:

Normal moves: Put the mouse cursor over the piece you want to move, push the mouse button, move the cursor to the destination, and let the mouse button up.
Castling: Move the king two squares left or right.
En passant captures: Move the capturing pawn diagonally as if doing a normal capture.
Pawns always promote to queens.
Switching sides: Type 'g' (for "go") with the mouse over the board to tell the computer to make the next move.
Takebacks: Type 'b' to take back a move.
Restart: Type 'r' to restart.