How to play

Fill the 9×9 grid so that every row, every column, and every 3×3 box contains the digits 1 through 9 exactly once. Each puzzle starts with some digits already given — those are fixed. Tap a cell, then tap a number to fill it in. Every puzzle here has exactly one solution, and none of them ever require guessing: careful logic is always enough.

Controls

• Click or tap a cell, then a number — or type 1–9 directly
• ↑ ↓ ← → — move between cells
• N — toggle notes (pencil marks)
• Z or U — undo (unlimited)
• Delete, Backspace or 0 — erase a cell
• H — use a hint (3 per puzzle)
• R — restart the puzzle

Strategy tips

• Scan for singles first. Look for cells where only one digit can go, and for digits that fit only one spot in a row, column, or box. Easy puzzles fall entirely to this.
• Use notes aggressively. Pencil in every candidate for the tricky regions. Most mid-game logic — pairs, locked candidates — only becomes visible once the notes are down.
• Look for locked candidates. If a digit's only spots in a box all sit on one row, that digit can be ruled out of the rest of the row — a medium-level workhorse.
• Never guess. Every puzzle here is graded by the techniques it needs and is solvable by logic alone. If you're stuck, there is always a deduction you haven't spotted yet.

About Sudoku

The modern 9×9 Sudoku was popularized in Japan in the 1980s under the name 数独 ("single digits") and became a worldwide phenomenon in the 2000s. Behind the simple rules sits real depth: valid grids number in the sextillions, and at least 17 given digits are needed for a puzzle to have a unique solution.

This edition ships 300 puzzles — 100 each of Easy, Medium, and Hard. Every board is generated with a guaranteed unique solution, then graded by the human solving techniques it requires: Easy puzzles fall to singles alone, Medium needs locked candidates and pairs, and Hard calls for triples and X-wings. Nothing ever requires trial and error.