Find a path that visits every square in the grid, avoiding walls and never crossing itself, only ending when you find yourself back at the beginning. In other words, create one continuous circuit. These circuits start off easy. But consider yourself warned: they don’t end that way.
Start with one of the simple 4×4 grids. Plot your moves carefully. Think ahead–not just by one square, but by four or five. If you think you’ve made a mistake, trace back over your line: it will disappear.
If you really get stuck, press Hints. The errant lines will turn red, then disappear.
If you can’t make headway, press Hints again. We’ll fill in a line for you.
When you’ve solved the puzzle correctly—and there is only one solution to every puzzle—you’ll know it.