How to play
Fill every cell with one of two symbols, shown here as a ring (0) and a dot (1).
No more than two identical symbols may sit next to each other in a row or a column.
Every row and every column contains as many rings as dots — three of each in a 6×6 grid, six of each in a 12×12.
No two rows are the same, and no two columns are the same.
Tap a cell to cycle empty → ring → dot → empty. On a keyboard, the arrow keys move, 0 and 1 place a symbol, Space cycles and Backspace clears. Puzzles of this type are also published under names such as Takuzu and Binairo.
Strategy and tips
- Doubles: two identical symbols side by side must have the opposite symbol on both ends.
- Sandwiches: when two identical symbols have one empty cell between them, that cell takes the opposite symbol.
- Counting: once a line holds its full quota of one symbol, every remaining cell in it is the other symbol.
- Start where one symbol crowds a line. A row of 8 that already holds three dots needs only one more; every empty cell that would make a fourth and a fifth impossible narrows down fast. Lines with many givens are usually the first to finish.
- On hard and expert sheets these three are not enough. Take a line that is nearly full and list the ways it could still be completed. Often only one of them avoids three in a row, or only one keeps the line different from a finished one.
- Work in passes. After every few placements, sweep all the rows and then all the columns again — new doubles keep appearing. The line logic guide has worked examples.
Questions
- Which symbol is 0 and which is 1?
- The ring stands for 0 and the dot for 1. The puzzle itself doesn’t care — only the patterns matter.
- What changes between the levels?
- Easy is 6×6, medium 8×8, hard 10×10 and expert 12×12. On easy and medium, the no-three rule and the balance rule are always enough. Hard and expert sheets require the stronger step where only one way of finishing a line remains, including the rule that lines can’t repeat.
- What does the hint tell me?
- It finds the next cell that logic forces in your current position and names the rule behind it, such as No three in a row or Line balance.
- Why can’t two lines be identical?
- Without that rule, many grids would have more than one solution. With it, every sheet here has exactly one, and on hard and expert sheets the rule is part of the logic: a nearly finished line that could become a copy of a finished line must be completed the other way.
- Is my game saved?
- Yes. Every move is saved in this browser, so you can close the tab and continue later. Undo goes back as far as you like, even after a reload.