Binary Grid Puzzles
How it works
A binary grid puzzle is a square or rectangular grid where every cell holds one of two symbols. A few cells are given at the start, and you fill in the rest. The rules are short. No three of the same symbol may sit side by side in a row or a column. Every row and every column holds as many of one symbol as the other. In many versions, no two rows may be identical, and no two columns either. Some puzzles add small marks between cells that say two neighbours must match or must differ.
You solve it with a handful of patterns. Two alike in a row means the cells on either side must be the other symbol. Two alike with a gap means the gap is the other symbol. Once a line has its half of one symbol, the rest of it is the other. Each placement feeds the next, so a board that looks empty at first fills up quickly once the first few cells fall.
What makes a good one
- One answer, reachable by reasoning alone, with no guessing.
- Two symbols that differ by shape as well as colour.
- A clear warning when a line breaks a rule, without giving away the answer.
- Hints that name the deduction instead of just filling a cell.
- Boards big enough to be interesting and cells big enough to tap on a phone.
Strategies that help
Look for pairs. Two alike next to each other force both ends of the pair. This is almost always the first move.
Fill the gaps. Two alike with one empty cell between them means the middle is the other symbol.
Count every line. When a row has all of one symbol it needs, fill the rest with the other straight away.
Compare nearly full lines. If two rows differ in only two empty cells and identical rows are not allowed, you can often tell which way round those two cells go.
Our take
Our binary grid puzzle is Lampline. Every cell is a signal lamp that shows a Dot or a Dash, a Keeper’s Logbook explains the next deduction in words, and a Daily Signal of two boards is the same for everyone. If you like grid logic with a different rule, see region logic puzzles.