public State toggleState() {
		if (revealed) return null;
		
		switch(state) {
		case flagged:
			state = Minesweeper.questionMode ? state = State.questioned : State.unmarked;
			break;
		case unmarked:
			state = State.flagged;
			break;
		case questioned:
			state = State.unmarked;
			break;
		default:
			//do nothing
			break;
		}
		
		return state;
	}