Grid Clues

Each row and column carries the lengths of its filled runs, in order. A row marked 2 1 has a block of two, then a gap, then a single. Work out which squares must be filled — every puzzle here is checked to have exactly one answer, so you never have to guess.

It runs entirely on your device: 0 network requests, works offline. No ads, no account, nothing to buy, and no betting, money or prizes of any kind.

1. Focus the board — click it, or press Tab until it is focused.
2. Move with the arrow keys.
3. Press Enter to cycle a square: blank → filled → marked empty → blank.
4. Marking is free. Only filling a square that should be empty costs one of your three tries, so marking is the safe way to record something you have worked out.
5. Finished clues dim, so what you have already settled stays visible on the board.

How do you solve a nonogram without guessing?

Start where the clue leaves the least freedom — the edges and the big numbers. On a five-wide row, a clue of 5 fills the whole row and a clue of 4 forces the middle three squares whichever way it sits, because those three are covered by every possible placement. That overlap trick is the engine of the whole puzzle: slide the block to its leftmost position, slide it to its rightmost, and anything covered both times is certain. Fill those, mark the squares that are now impossible, and the new information usually forces something in the crossing direction.

Is every puzzle solvable without a guess?

Yes, and it is verified rather than assumed. A random picture is drawn, its clues derived, and the puzzle is kept only if a solver finds exactly one grid matching them — it counts to two and stops. Most random pictures are ambiguous and are discarded; only the unique ones are dealt.

What does marking a square empty do?

Nothing to the score — it is a note to yourself, and it never costs a try. It matters because these puzzles are solved as much by ruling squares out as by filling them in, and a deduction you have to keep in your head is one you will make twice.

Why is a wrong fill punished but a wrong mark is not?

Because filling asserts something about the picture and marking asserts something about your reasoning. Getting a fill wrong means the board no longer shows the truth, so it is refused and counted; marking is always reversible and always free.

Does it work offline?

Yes. Once the page has loaded once, the whole game — including the generator and the uniqueness solver — is on your device. There is no server involved in play at any point.

Is there any money, betting or in-app purchase in this?

None, and there never will be. No currency, nothing to buy, no hints to unlock for a fee.

Can I play it with a keyboard or a screen reader?

Both. Arrows move, Enter cycles the three states, and every square announces its row, column, state and its row clue. The three states are three different glyphs, so nothing depends on colour.

Five by five, typically eight to eighteen filled squares, and three wrong fills allowed. Uniqueness is checked at generation time by an exhaustive line-based solver, not estimated.

Light Grid is the other deduction puzzle here — it turns on parity where this turns on overlap.

Bookmark this page (Ctrl+D, or ⌘D on Mac) or install the app — it works offline the next time you need it.