Kakuro

Einstein is our highest difficulty, and every puzzle carries a guarantee: solvable through pure logic, no trial and error needed. Our constraint propagation engine verifies each puzzle before publishing. If there's a solution, there's a logical path to it.

You'll need every technique: forced combinations, cross-entry elimination, combination filtering, naked singles, and careful systematic reasoning. The solving path is rarely linear. You might fill a few cells with basic techniques, stall, then find that filtering combinations on a specific entry unlocks a chain of placements across the grid.

These puzzles take time. A solve under 20 minutes is fast. If you need the full hour, that's normal. For technique refreshers, check the strategy guide.