Nonogram

Nonogram — how to play and tips

Nonograms — also called Picross or Griddlers — are logic puzzles solved with numbers rather than guesses. The clues along each row and column tell you the lengths of the filled runs in that line, in order. Work out which squares must be filled and which must be empty, and the grid resolves itself into a picture without you ever needing to take a blind stab at a square.

Reading the clues

A row clue of 4 2 means: somewhere in that row there is a block of exactly four filled squares, then at least one empty gap, then a separate block of exactly two filled squares — and nothing else anywhere else on the line. The gap between the two blocks can be one square or several, which is exactly what makes the puzzle interesting rather than mechanical. A clue of 0 means the entire line is empty, and it's a real, deliberately generated clue rather than an absence of one. Column clues work identically, just read top to bottom instead of left to right, and every finished grid has to satisfy both directions at once.

How to play

Tap a square to fill it in. Drag across several squares to paint them all in one stroke — the very first square your drag touches decides what the whole stroke does: if that square was empty, the drag fills every square it crosses, and if it was already filled, the drag clears them instead. That one rule is what stops a diagonal or careless drag from leaving a messy, half-toggled mix of filled and empty squares behind it. Switch to the Mark tool to place an X on squares you've logically proved must be empty; marks are purely your own working notes, are never compared against the hidden picture, and can be painted or cleared with drags exactly the same way fills can. On desktop, F switches to Fill, X switches to Mark, and C clears the entire board back to empty in one press.

A row or column's clue numbers visibly dim the instant that line's filled squares match its clue exactly, and they light back up if a later edit breaks that match. That dimming is genuinely the most useful feedback a nonogram can give you mid-solve — it confirms a line is completely finished without handing you any information you hadn't already worked out yourself, which keeps the puzzle honest. The heads-up display also counts down a running total of lines left to satisfy, so you always know roughly how much of the grid remains unresolved even on a busy 15×15 board.

Any valid solution counts

Some clue sets genuinely allow more than one legal picture — the numbers pin down the run lengths in each line but don't always pin down a single unique arrangement across the whole grid. Most nonogram implementations only compare your finished grid against the one specific pattern that was used to generate the clues in the first place, which means a player who logically deduces a different but completely valid picture gets told they're wrong while staring at a grid that satisfies every single clue on the board — arguably the single most frustrating bug a logic puzzle can have, since the player did nothing wrong.

This version checks the actual rule instead of a stored answer key: you win the instant every row and every column's filled squares match that line's clue, computed fresh from your live grid every time you paint a square. Any legal solution is accepted on the spot, so that failure mode simply cannot occur here, and no separate uniqueness-checking solver is needed to guarantee it.

Sizes and daily mode

Mini 5×5 takes well under a minute once you know the technique and suits a quick break. Classic 10×10 is the standard-length puzzle and the default size. Large 15×15 is a proper sit-down solve with enough lines that keeping track of partial deductions by eye starts to matter. Best completion times are tracked and saved separately for each size, so a fast Mini time and a slow Large time don't compete with each other. The daily puzzle is generated from a seed built out of the calendar date in UTC, so every player worldwide is solving the identical grid on any given day — and, importantly, each size has its own separate daily rather than three views of one shared grid, so the daily Large puzzle is a genuinely different picture from the daily Mini.

Solving technique

Start with the largest clues on the board. In a row that's 10 squares wide, a clue of 8 means the block of eight filled squares must overlap the middle six squares no matter which end of the row it starts from — slide it as far left as it goes and as far right as it goes, and the squares common to both positions are guaranteed filled. That technique is called overlap, and it's the standard opening move on any line whose single clue is more than half the line's length. Once you've placed the certain overlap squares, use marks aggressively on the squares you've ruled out: proving a square is empty narrows down the possibilities for its row and column just as much as proving one is filled, and a grid with its dead squares marked off makes the next deduction visually obvious instead of something you have to hold in your head. Working the intersections between a freshly solved row and its columns — or vice versa — is usually where the next available deduction is hiding once the obvious overlaps are used up.

Playing on desktop and mobile

The board and clue layout scale to fit the screen automatically, with the number gutters sizing themselves to however many clue digits the longest row or column actually needs, so a 15×15 puzzle with long clue lists doesn't crowd the grid on a small phone screen. Touch play is built around the drag-to-paint gesture described above, which is precise enough for filling long straight runs with a single swipe; the Fill and Mark buttons sit in a toolbar above the board so switching tools never requires reaching for a keyboard. On desktop, the F/X/C keyboard shortcuts let you keep one hand on the mouse for painting and the other for switching tools and clearing mistakes, which is noticeably faster once you're solving Large puzzles regularly.