void setTouched(int tt) {
		map[tt] |= VISIT;
		if ((map[tt] & NEB) == 0) { // no bomb around, auto flip
			for (int i = 0; i < 8; i++) {
				if ((map[tt + directions[i]] & VISIT) == 0) { // 已翻開就不用再做了
					setTouched(tt + directions[i]);
				}
			}
		}
	}