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A little logic. A satisfying break.

How to play Binary (Takuzu)

Two values, three rules. Fill the board with zeros and ones using deductions, one cell at a time.

Play Binary

Already playing in another tab? Switch back to keep your board and Undo history. These examples are separate from your puzzle.

The three rules

  1. Every row and column has equal numbers of zeros and ones: three of each on a 6 × 6 board, four of each on an 8 × 8 board.
  2. No row or column contains three consecutive equal values. Two equal values together are allowed.
  3. Every completed row differs from every other row. Every completed column differs from every other column.

Bold starting clues are fixed. A zero is a filled cell, just like a one. Empty cells have no value. Diagonal lines do not matter.

Two worked examples

Before

After

Action: Enter 1 in column 3: three consecutive zeros are forbidden.

Stop a triple

0 0 □ becomes 0 0 1. A third zero would break the no-triples rule. Likewise, 1 □ 1 needs a zero in the gap. The same patterns work vertically.

Balance a line

On a 6 × 6 board, 0 1 0 0 □ □ already contains three zeros. Both remaining cells must be ones, giving 0 1 0 0 1 1. Check their columns too: a conflict means an earlier entry needs rechecking.

Build one deduction at a time

  1. Scan for adjacent pairs and equal values separated by one gap.
  2. Count zeros and ones in nearly full rows and columns.
  3. Compare a line with two gaps to completed parallel lines. It must remain different.
  4. For a harder line, consider all completions allowed by its balance and triple constraints. A cell shared by all those patterns is forced.

A plausible guess is not a proof. Use Check or Undo if the board stops making sense.

Checked hint rules

Triple Avoidance

Prevent three equal values consecutively in a row or column.

Line Balance

Each completed line contains equal counts of both values.

Completed Line Distinctness

An incomplete line must differ from every completed parallel line.

Builds on: Line Balance

Line Pattern Consensus

If every legal completion of a line agrees on a cell, that value is forced.

Builds on: Triple Avoidance Line Balance Completed Line Distinctness

Controls & hints

Ctrl+Z or Command+Z undoes the last edit or whole applied hint. Ctrl+Shift+Z or Command+Shift+Z redoes; Ctrl+Y also redoes. These work from the active board and its action buttons. Text fields keep their native editing shortcuts. Settings saves this game’s optional timer and Auto-check choice independently. Turn Auto-check off and use Check when you want to review your work.

Tap or click a cell, then choose 0, 1 or Erase. On a keyboard, use arrow keys to select a cell, Space to cycle blank → 0 → 1 → blank, 0 or 1 to enter directly, and Delete or Backspace to erase. Hold-to-repeat and modified Space do not enter values. Starting clues cannot be edited. Space saves every edit immediately, but checking and challenge mistakes wait until you leave that cell or choose Check. Only the final value is checked; cycling through a wrong value does not cost a mistake. Hint first settles the cell and then checks the current board. Pause or leaving the page also settles it. Undo cancels the pending edit.

Get a hint checks your current entries before explaining an actual rule. Outlined support cells show where to look; the action names the target row, column and value. Apply enters that value once. Undo and Redo work on entries, erasures, restarts and applied hints. Editing or changing the board makes an earlier hint unusable.

Progress saves locally as you play. Your boards brings all your games together, latest played first. Share a code or link to the original puzzle; download progress to move your entries and timer. Restoring a download asks before replacing progress. If another tab changes a save, recovery controls keep both copies available.

Sizes and difficulty

Choose 6 × 6 or 8 × 8 at Easy, Medium or Hard, or 10 × 10, 14 × 14 or 20 × 20 at Easy or Hard. Easy uses triple avoidance and balance. Medium also needs completed-line distinctness. Hard needs line-pattern consensus. On the larger boards, Hard also requires repeated independent consensus reasoning, supporting deductions and substantial work left after both easier repertoires. These conditions are checked in two fixed solving orders. These labels describe checked techniques, not a human or publisher difficulty calibration.

Relaxed play has no mistake limit. The optional three-mistake challenge checks entries and lets you continue relaxed after three mistakes. The timer is optional and pauses when the board is hidden or paused.

Questions

Is Takuzu the same game?

Yes. Binary puzzles are also known as Takuzu. Here the values are always shown as 0 and 1.

Can zero mean empty?

No. A visible 0 is an answer or a fixed clue. Use Erase to return an editable cell to blank.

Is there a daily Binary puzzle?

Binary currently offers New, Next and saved or shared boards. Today’s Binary and the published archive offer shared puzzles when available.