In challenge 2 you are not allowed to visit the same grid point twice (neither as an endpoint nor as an intermediate point of a segment).
In challenge 3 you have to find a closed polyline that visits all grid points. Here you are allowed to visit any grid points more than once, but note: There is a solution that (apart from the start- and endpoint) visits no grid point twice. Can you find it?
Challenge 4 is free play: just connect all the grid points. Explore the various ways to do this. The segments do not have to vary in length.
The grid points are meant to be ideal points (with an infinitely small diameter).
A win message appears when you have solved the puzzle.
If you click the same point twice by accident, it will turn red. Click the "delete last stored" to undo the move.