public void undo() {
if (moveHistory.size() > 0) {
unmove((Move) moveHistory.lastElement());
moveHistory.removeElement(moveHistory.lastElement());
} else {
controller.alert("You haven't made any moves yet!");
}
}
public void addToHistory(Move move) {
// Add the move to the moveHistory so we can undo it later, if requested.
moveHistory.addElement(move);
}