Equal 0s and 1s
In Binary Puzzle every row has equally many 0s and 1s, and every column does too. On a 6×6 board that means three of each. On an 8×8 board it means four of each.
If a line already has all of one symbol, the leftover cells are the other. That is the fastest fill on a Beginner board. Count what is already there before you hunt for harder patterns.
The equal-count rule works with the other three: no three identical in a line, and every row unique, every column unique. You cannot put the leftover 0s into a clump of three.
A puzzle is solved when every cell is filled and each line has its half. Play Binary Puzzle. How to play Binary Puzzle.