Quite a brain teaser. On Planarity you have blue dots (called vertices) connected by lines (called edges). You basically have to reorganize the vertices by dragging them around so that no two lines intersect.
Planarity is one of many Puzzle Games to play online on your web browser for free at KBH Games. Tagged as Puzzle Games. Upvoted by 17 players. Other games you might like are Frogger and Strategy Defense 3. No download or installation needed to play this free game. Hope this game brings a little joy into your daily life.