Untangle starts as a knot: a ring of dots joined by lines that cross all over the place. Every knot it gives you can be laid out flat, with no two lines crossing, and your job is to find that layout by dragging the dots. Lines that still cross are easy to spot, and the puzzle tells you the moment you have it.
It comes from Simon Tatham's Portable Puzzle Collection, a set of small logic puzzles that has been maintained since 2004. The Type menu changes the number of dots, and New game makes a fresh knot every time, so it never runs out.
Controls
Drag a dot with the mouse or a finger. The menu bar has New game, Restart, Undo, Redo and Solve; Type changes the number of dots.
Genre
Puzzle, Logic, Touch, Relaxing
Price
Free — no account, no download, nothing to install
Tips for Untangle
Pull the dots with the most lines out to the edge first.
Find a triangle of three joined dots and build the rest around it.
Start with the smallest size in the Type menu and move up when it feels easy.