Untangle — free browser game

Your goal is to drag the scattered nodes (the dots) around the screen and rearrange them so that the strands between them no longer cross at any point. This classic graph puzzle, known in computer science as 'planarity', has been mathematically proven to have a solution at every level, so there is no such thing as an 'impossible level' — you just have to find the right arrangement. Grab a node with the mouse or your finger and drag it; as the nodes move, the strands attached to them move too, and any strands that cross each other are marked in red. When the crossing counter in the top corner drops to zero the level is complete and you advance to the next, more node-heavy level. The rules are simple but the strategy runs deep: the best approach is to first establish the outer perimeter, arrange the outer-ring nodes in a circle, and then untangle the inner connections. Another tactic is the 'flower technique': place the node with the most connections at the centre and fan the rest out around it according to their connection directions. If nodes get too close together they become visually tangled; to work comfortably, spread them across a wide area first, then bring them into the pattern you want. Your best score and the number of solutions up to your level are saved in your browser; the goal is to solve in fewer moves and beat your personal record.