Binary Puzzle
Two digits. Three little rules. Room to think.
Your puzzle saves in this browser.
Preparing your puzzle…
Select a square, then choose 0, 1 or Erase. Arrow keys move; 0/1 enter a digit, Delete clears. Enter or Space cycles blank → 0 → 1 → blank. U undoes, R redoes, H gives a hint, P pauses.
Your achievements · eight little milestones
Two digits. One satisfying pattern.
Fill the empty squares with 0 or 1. In every row and every column, exactly half the digits must be zeros and half must be ones. Three identical digits may never appear consecutively horizontally or vertically. Finally, every complete row must differ from every other complete row, and every complete column must differ from every other complete column.
A row is allowed to match a column: only rows are compared with other rows, and columns with other columns. Matching partial lines are fine until both lines are complete. Printed clues remain fixed. A full board wins only when all three rules are satisfied.
Easy controls, at your pace.
On a phone, select a square and use the large 0, 1 and Erase buttons. On desktop, click a square or move with the arrow keys, then type 0 or 1. Delete and Backspace clear an editable entry. Enter or Space cycles the selected square through blank, zero and one. The 6 × 6 grid is a compact starting point; 8 × 8 gives the same classic rules more room.
Undo and Redo revisit up to 200 entry changes. A new entry after Undo starts a new branch. Pause stops the active-play timer, and Full screen keeps the board and controls together. There is no time limit, mistake strike system or timed loss.
Useful hints, clearly explained.
Hint fills one verified digit and explains it. Equal pairs need an opposite digit at their edge, a gap between matching digits needs the opposite digit, and a row or column with its full quota of zeros needs ones in the remaining spaces. When a complete-solution check is needed, the hint is explicitly called a Verified value reveal rather than a simple deduction.
Visible rule conflicts are highlighted immediately. Check entries also compares your entered digits with the puzzle’s unique solution and highlights wrong entries. This is assistance, just like Hint. If the current entries cannot lead to a solution, Hint asks you to undo an uncertain entry or use Check. Restart keeps Hint and Check use recorded for the same attempt.
Original puzzles and progress that stays yours.
This edition uses 24 original uniquely solvable puzzle bases for each grid size. Seeded rotations, reflections and digit complements create variations while preserving all rules. Every base has been checked with two independent solution-counting methods. Grid size describes the amount of space to solve; we do not claim a standardized difficulty grade or that every puzzle can be finished with only the three simple hint techniques.
Your puzzle, entries, Undo/Redo history, selected square, active-play time and eight achievements save in this browser when storage is available. Another browser or device has its own progress. If saving is unavailable, the game still works; keep the tab open to keep that puzzle. Celebrations stay in a reserved strip away from the grid, and reduced-motion preferences are respected.
Stars mark real entries, balanced lines, completed grid sizes and repeated completed attempts. A no-assistance star requires a win without Hint or Check. Undoing the last entry and winning again, restarting, or reloading the same completed attempt cannot create another win.
Why is a square highlighted?
A warm highlight marks the selected square. Green marks a hinted entry. A coral highlight marks a direct rule conflict, or an entry flagged by Check. Immediate rule checks do not reveal every wrong guess; a wrong guess may fit nearby rules while preventing the full puzzle from being solved.
Can I change a printed clue?
No. Given digits stay fixed. Select an editable square and use the keypad or your keyboard instead.
Are two equal partial rows forbidden?
No. Only complete rows or complete columns are compared for uniqueness. You can continue filling a partial line that temporarily resembles another.
Does Undo remove the fact that I used a hint?
No. Hint and Check assistance stays recorded through Undo, Redo, Restart and saved reloads of that attempt. A new puzzle starts a fresh attempt.
Does every new puzzle have entirely new clues?
The site varies its original bases using rule-preserving transformations. A familiar base or variation can appear again. Every displayed puzzle still has exactly one solution.