Sudoku

Einstein is the hardest difficulty we offer, and every puzzle at this level carries a guarantee: solvable through pure logic, no guessing required. That means somewhere in the grid, there's always a deduction waiting — even when the board looks impossibly sparse and nothing seems to work.

You'll need the full toolkit here. Scanning, hidden singles, naked and hidden pairs, pointing pairs, box/line reduction, X-Wings — sometimes all in the same puzzle. The solving path is rarely linear. You might place three cells with basic scanning, hit a wall, find a pointing pair that unlocks two eliminations, then spot an X-Wing that breaks the entire middle section of the grid open. Jumping between techniques is the norm, not the exception.

These puzzles start with around 22 to 24 clues — barely a quarter of the grid filled in. The opening move is almost always the same: fill in complete candidate lists for every empty cell, then start hunting. Check for naked singles first (fast wins), then hidden singles, then pairs, then the advanced techniques. Be methodical. Resist the urge to guess — guessing at this level will compound errors fast and force a restart.

When you solve one of these cleanly, with no hints and no solution reveal, you'll know it. It's the most satisfying solve in the game. For a walkthrough of every technique used at this level, see the full strategy guide on the Sudoku hub page.