The puzzle
A graph is drawn with its edges crossing all over each other. The graph is planar, so a layout with no crossings exists. You drag the vertices around until you find it.
Where it came from
I met the puzzle at a Sword Art Online event in Kabukicho and had it running a few days later, then built a game around it. I work fastest right after something has delighted me.
What is in it
01Drag-and-drop vertices.
02Edge crossings detected in real time as you move them.
03Levels that get harder as you go.