How to play binary puzzle
- Look at the grid. Each cell is empty, 0 or 1 on a wooden board. This page ships 14 hand-checked levels from 4×4 to 8×8 (260 empty cells in total across all boards).
- Tap to cycle 0 and 1. Tap an empty cell to place 0, tap again for 1, tap once more to clear. Given digits (darker rim) stay locked.
- Satisfy the four rules. Equal number of 0s and 1s in every row and column; no three identical digits in a row or column; all rows unique; all columns unique.
- Use Undo, Reset or Hint. Undo reverses the last fill. Reset clears your entries. Hint fills one forced (or solution) cell — games that used Hint do not update your best.
Binary puzzle strategy
- Never place a third identical digit when two already sit side by side — and watch for the sandwich pattern XX_ / _XX that forces the opposite digit.
- When a row already has n/2 zeros (or ones), every remaining blank in that row must be the other digit.
- Near the end, compare almost-finished rows: two rows may not match, so the last blanks are often forced.
- If a line looks stuck, Undo a few fills instead of Reset; most early mistakes are local.
- Hint always fills a cell consistent with the unique solution, so following it will finish a solvable board.
Why every level is uniquely solvable
We build a full legal 4×4+ grid (equal counts, no triples, unique lines), then remove cells one by one only while a backtracking solver still finds exactly one completion. That is the same uniqueness check used in the unit tests.
Hint prefers forced cells from those rules; if several options remain, it reads the stored unique solution — never a second conflicting fill.
More logic puzzles
Like grid logic? Try star battle, tents, Lights Out, Fillomino, LITS, ball sort or one line. Chinese speakers can play the 二进制谜题 version of this page with the same saved progress.