Takuzu

The board and the three rules

The grid is N×N, and N is always even — 6×6, 8×8 or 10×10 depending on the level. Each square holds 0, 1, or nothing yet.

The same digit is never allowed three in a row, each row and column holds exactly half 0s and half 1s, and no two rows may read alike — nor may two columns.

• You win the moment every square is filled and none of the rules above is broken. There is no comparison to a hidden solution behind the scenes — filled and rule-clean is the whole test.
• There is no mistake limit, no lives and no game over. A wrong digit costs you nothing but the time to change it.

Controls

• Tap a square to cycle it: empty → 0 → 1 → empty. That is the entire interface — one gesture, no modes.
• Squares that started with a digit are fixed and cannot be changed. Tapping one does nothing.
• There is no long press and no mode switch. Nonogram needs both, because painting and marking × are two different kinds of mark — but the states in Takuzu sit on a single cycle, and every step of it is the same action: placing a digit.

Adding a second gesture where there is no branching action would only give you more to remember, not more to do.

Sizes, levels and the Daily

• There are three board sizes: 6×6 for the earliest levels, 8×8 for the middle band, and 10×10 for the highest band. Odd sizes are not offered, because a row of odd length cannot be split into equal halves of 0s and 1s. Boards of 12×12 or larger are not offered either, since each square would drop below a comfortable fingertip.
• The share of starting digits drops as you climb within a band, then steps back up at the start of the next one — a bigger board is harder even at the same share, since it takes a longer chain of reasoning to reach the same conclusions.
• Levels run 1–100 and unlock in order. Any level you have unlocked can be replayed, and it is always the exact same board — nothing is downloaded, every board is generated on your device from a seed.
• The Daily puzzle is one per day, always 8×8 with 23 starting digits — 36% of the board. The last 30 days stay open regardless of order, and finished days are recorded, but no streak is ever counted or shown.

The no-guess promise, and Hint

Every puzzle here can be finished with three techniques, and no others. A run of three squares with two matching digits and one gap forces that gap to the opposite digit. A line where one digit has already filled half its squares forces every remaining square to the other digit. And a line with only two undecided squares, needing one 0 and one 1, is settled by comparing it to a finished line in the same direction that already matches everywhere else — the no-duplicate rule allows only one of the two arrangements.

A puzzle is only used if repeating those techniques settles the entire grid — never guessing, and never leaving two arrangements both legal. That also means the solution is unique.

• Hint is unlimited and free. It shows one square these techniques can settle right now, and highlights the row or column that proves it.
• If a row or column currently breaks a rule, the hint points at that line first — building a deduction on top of a broken line would not be help.
• There is no Undo. Every tap is already reversible: the same square cycles back through 0, 1 and empty. Adding Undo would only give you a second way to do what one tap already does.

Sudoku keeps Undo because placing a number there erases pencil notes in the same row, column and box, and a single tap cannot bring them back. Takuzu has no notes to lose, so that reason never applies here.

Violations, not answers

Violations are shown at all times, one per rule. Three squares in a row sharing a digit are marked the moment the third one lands. A digit that has already passed half its row or column is marked before the line is even full — once it passes half, that line can no longer be completed legally. And two finished lines in the same direction that read alike are both marked, but only once both are actually full.

• None of this compares your board to a hidden solution. A digit that breaks no rule is never flagged, even if it will turn out to be wrong.
• Sudoku has a Show Mistakes toggle, on by default, because a Sudoku square only ever has one right answer to compare against. A Takuzu square only ever holds two possible digits, so an unbroken guess is not yet a mistake — it is only not-yet-contradicted, and marking it red would be revealing the answer rather than the logic.

Because there is nothing here to remember across boards, this game keeps no settings of its own.

Tips

• Scan for two matching digits sitting next to each other. The empty square before them, after them, or caught between two matches, is forced to the opposite digit.
• Count each row and column as you go. The moment one digit reaches half the squares, every square still empty in that line takes the other digit — no more guessing needed there.
• When a line is down to its last two empty squares, check it against every finished line running the same way. If they already match everywhere else, the no-duplicate rule tells you which digit goes where.
• Work rows and columns in turn. Finishing a row often completes the count or breaks a tie in a column, and the reverse is just as true.
• Stuck? Take a Hint — it is free and unlimited, and it will point at whichever line still has something to give.

Questions people ask