https://doujinblog.org/%e5%90%8c%e4%ba%ba%e3%82%b2%e3%83%bc%e3%83%a0151229-limit-cycle-%e3%83%89%e3%83%a9%e3%82%b4%e3%83%b3%e3%81%a8%e9%bb%92%e7%ab%9c%e3%81%ae%e5%b7%ab%e5%a5%b3/