This weekend I discovered a webpage that generates these puzzles, where the goal is to draw the unique closed loop in a square grid, subject to constraints on how many times you are allowed to pass next to certain tiles. There are various difficulty levels, and you can also choose among many other tilings (even the hat monotile!). These are very satisfying to solve, but I also find them quite addictive, so try them at your own peril!
https://www.chiark.greenend.org.uk/~sgtatham/puzzles/js/loopy.html





