Slitherlink

Einstein is the highest difficulty. Each puzzle is a 14×14 grid, and every one carries a guarantee: solvable through pure logic, no trial and error needed. Our edge-probing certifier verifies each puzzle before publishing.

You need every technique at once. Zero elimination, corner patterns, adjacent 3-3 and 3-0, edge counting, vertex constraints, loop closure prevention, and region parity analysis. The solving path mixes strategies constantly — there is no single approach that carries you from start to finish.

A clean solve under 20 minutes is fast. An hour is normal. For pattern refreshers, the tips & patterns page covers everything.