Sudoku

It's literally just Sudoku.

I enjoy playing some sudoku games on my phone, but they're absolutely riddled with ads - so, I've made a version without them.

Features

• Six difficulties, from Beginner to Master. Harder levels give you fewer starting numbers and need smarter solving techniques. Every puzzle has exactly one solution.
• Unlock as you go: win a difficulty a few times to unlock the next one.
• Mistakes count: a wrong number turns red and adds a strike. Hit the limit and the puzzle's over. The harder the puzzle, the less mistakes you can make.
• Notes: pencil in the numbers a cell could be. Correct answers clear themselves from your notes automatically.
• Timer and best times for every difficulty.
• Share puzzles with friends: every puzzle has a code like HARD-K9ZQ2T. Anyone who enters it gets the exact same grid, so you can compare times. Shared codes skip the unlock requirements.
• Undo, erase, number highlighting, and dark mode.

Mobile supported! Big tap targets, works held upright or sideways, and plays fine on desktop too.

Keyboard controls (desktop): 1–9 to enter numbers, arrow keys to move, N for notes, Backspace to erase, U or Ctrl+Z to undo, Space to pause.

Your progress and any unfinished puzzle are saved in your browser, so you can close the tab and pick up where you left off. Saves live in each browser, so playing on your phone and then your PC means two separate sets of progress, and clearing site data wipes them.