The classic number puzzle with a modern twist. Four difficulty levels, pencil notes, hints, undo and a timer — every game is a fresh puzzle with exactly one solution.
Keyboard: arrows move · 1–9 place · N notes · H hint · U undo · ⌫ erase — your game is saved until you close the tab.
The board is a 9×9 grid divided into nine 3×3 boxes. Some cells come pre-filled with digits — these are your clues and cannot be changed. Your job: fill every empty cell so that each row, each column and each 3×3 box contains the digits 1 to 9 exactly once.
Three rules of thumb that solve most easy puzzles: start with the row, column or box that has the most digits; look for cells where only one digit can legally fit; and use pencil notes (✏) to keep track of candidates. When you place a digit, the notes in the same row, column and box are cleaned up automatically.
Easy ≈ 41 clues · Medium ≈ 34 · Hard ≈ 28 · Expert ≈ 24 — fewer clues, harder logic
Every puzzle here is generated on the spot and verified to have exactly one solution — no guessing required, pure logic always works. Your progress, notes and timer survive a page refresh (until you close the tab), and 3 hints per puzzle reveal a cell when you are stuck.
The entire game — generation, solving and playing — runs locally in your browser. Nothing is sent to any server or stored anywhere.
Fill the 9×9 grid so every row, every column and every 3×3 box has the digits 1–9 with no repeats. Start on Easy (about 41 clues): find a row, column or box that is nearly complete and deduce the missing digits. Tap a cell, then tap a number to place it.
Difficulty comes from how many clues you start with: Easy gives ~41 pre-filled digits, Medium ~34, Hard ~28 and Expert only ~24. Fewer clues mean longer deduction chains and advanced techniques like naked pairs and box-line reduction.
Yes. Each puzzle is generated by removing digits from a complete valid grid, and every removal is verified by a solver to keep the solution unique. If a removal would allow a second solution, the clue is put back.
Notes (the ✏ button) let you mark small candidate digits in a cell. They are essential from Medium upward: track what could go where, and the puzzle practically solves itself as options get eliminated. Placing a digit automatically erases that candidate from related notes.
Yes — your board, notes, timer and mistake count are kept in the browser's session storage and restored when you come back. Closing the tab starts a fresh puzzle (that is the point of session storage: nothing lingers).
Yes: arrow keys (or WASD) move the selection, 1–9 place digits, N toggles notes, H uses a hint, U undoes and Backspace erases. On phones, simply tap cells and use the number pad.