“Arrange the vertices such that no edges overlap”
Planarity is a game that is simple in concept, but will have your visual processing areas tying themselves in knots. All you have to do is rearrange a bunch of vertices so that none overlap (creating a planar graph). It starts off simple but gets complex very quickly.
Edit: Duh. Forgot to include a link in the original post.
Wasn’t too many levels before I was hopelessly tangled…