https://e621.net/posts/2721717?q=zero-sum
https://static1.e621.net/data/d0/8e/d08e837154f0370c9c1ce916992dbf8a.webm
FULL-https://static1.e621.net/data/ab/d8/abd8e964af4bf319a26483e8b9580267.webm
https://static1.e621.net/data/92/b6/92b6c18472d948988b3e7cfcc4b24e13.webm