How the binary puzzle works

A binary puzzle is a grid-deduction game played with just two digits. Each row and column of the even-sided grid must end up with exactly half 0s and half 1s, no digit may appear three times in a row horizontally or vertically, and no two rows — or two columns — may be identical. From a scattering of given digits, logic alone completes the board.

People sometimes call it binary Sudoku, and the comparison is apt: like Sudoku it's a constraint puzzle with a unique solution, but with an alphabet of two, so you can learn it in a minute and carry every rule in your head from the very first game.

The two-digit alphabet is deceptive. Small boards are quick, but as grids grow the three rules interlock — a placement in one row ripples through the columns it crosses, and the strongest solvers work whole lines at a time.

From first move to hard boards

Your first tools are pairs and sandwiches: two adjacent 1s must be flanked by 0s, and a 1_1 gap must take a 0 (and vice versa). Add counting — once a row has its quota of one digit, the remainder fills itself — and easy boards fall.

Medium boards need advanced counting: consider every legal way a line could be completed, and fix the cells all completions agree on. Hard boards require the duplicate-line rule — eliminating a candidate completion because it would copy a finished row or column. Our difficulty tiers are graded by exactly these techniques, so the label on the tin matches the logic inside.

Start with today's daily board, or pick a size from 6×6 to 14×14 in the unlimited collection — all 600 boards free, no account needed.