Zen Sudoku
The goal. Fill the whole 9×9 grid so that every row, every column, and each of the nine 3×3 boxes contains the digits 1 to 9 exactly once — no repeats anywhere.
Placing numbers. Tap a cell to select it, then tap a number on the pad below. On a keyboard: press 1–9 to place a digit, Backspace or Delete to clear a cell, and the arrow keys to move around the grid.
Notes (pencil marks). Tap Notes (or press N) to switch into note mode, then tap numbers to jot down candidates in the corners of a cell. Placing a real number automatically erases that candidate from the same row, column and box.
Highlights. When you select a cell, its row, column and box are shaded, and every cell that already holds the same number lights up in the accent colour — handy for spotting where a digit can still go.
Mistakes. A digit that doesn't belong turns red. You're allowed 3 mistakes — on the third, the game ends. The counter in the middle shows how many you've used.
Hints. Stuck? A hint (or press H) reveals one correct cell for you. You get 3 hints per game, shown on the button.
Difficulty. Six levels, from Beginner down to Master — the harder the level, the fewer starting numbers you're given. Your best time is saved separately for each level.
Keys: 1–9 place · Backspace erase · N notes · H hint · arrows move.
Three mistakes reached. Take a breath and begin a fresh grid.