Binary
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You have solved every puzzle at this level.
Tap a cell to cycle through 0, 1 and empty. With a keyboard, use the arrow keys, 0 and 1.
How to play
Write a 1 or a 0 in every cell. No three identical digits may sit side by side, each row and each column holds as many ones as zeros, and no two rows and no two columns are alike.
Solving techniques, step by step
Grid sizes
Every grid size has its own page with its own levels. A puzzle's level depends on which techniques it needs and how often.
Questions
- Does every puzzle have just one solution?
- Yes. Before a puzzle goes up, we check that it has exactly one solution and that our solver reaches it by logic alone.
- Will I ever have to guess?
- No. Every puzzle can be solved one logical step at a time. If you get stuck, the hint button shows the next step and explains why it works.
- Can I print the puzzles?
- Yes. Under every puzzle there is a link to a one-page PDF. The printout has no solution on it, and its link opens the same puzzle here, with hints.
- Does it work offline?
- Yes, after your first visit. The site keeps its pages and the levels you have opened in your browser, so they still play without a connection.
- Is it free?
- Yes. Every puzzle on the site is free to play. There are no ads and no accounts.
- Where is my progress saved?
- In your browser. Your progress, times and streaks never leave your device, and clearing this site's data in your browser deletes them.