2017-12-12 Z-turn boardのまとめ http://dora.bk.tsukuba.ac.jp/~takeuchi/?%E9%9B%BB%E6%B0%97%E5%9B%9E%E8%B7%AF%2Fz-turn%2F%E5%9F%BA%E6%9C%AC%E4%BA%8B%E9%A0%85