Kakuro

Einstein uses 11×11 grids and is our highest difficulty, with a guarantee: solvable through pure logic, no guessing. What sets Einstein apart is that elimination alone isn't enough — every puzzle requires what-if reasoning: assume a digit, follow the consequences, and rule it out when it forces a contradiction. Our logic engine verifies each puzzle before publishing.

You'll need every technique: forced combinations, cross-entry elimination, combination filtering, naked singles, and single-cell what-if 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.