Exact fit: account for the gaps
Before trying positions, work out how much room the clues require. Sometimes the runs and their separators use the whole line, leaving no decision about where anything goes.
LEARNING CENTRE
Nonograms: turn clues into certain squares
Learn to distinguish a filled square you can prove from a placement that merely fits. Start with one line, then carry its deductions through a full board. The exercises focus on the number clues; a picture you think you recognise is not evidence.
Rules you need at the board
Fill squares to match the ordered runs beside each row and above each column. Separate consecutive runs by at least one empty square. A clue of 0 means the line is empty. These compact boards practise number constraints; their patterns are not promised to depict recognisable pictures.
Four techniques to practise
Overlap: keep only what every placement shares
A run does not need a known starting point to force some squares. Compare its possible positions and look for the section that survives every choice.
Completed runs: prove the boundaries
Empty marks do real work. Once a run is known to be complete, its boundaries prevent it from growing and may constrain the next run.
Crossing information: let rows and columns help each other
A difficult-looking row may become simple after one column deduction. Revisit the lines touched by a new mark instead of repeatedly scanning the whole puzzle unchanged.
Follow a practice collection
1. Find the first certain squares
Work on uncluttered lines that separate exact fits from overlap. Compare a forced result with a similar line that still has choices, then explain why the difference matters.
2. Use the marks you already know
Carry proven squares into crossing lines and close completed runs. The emphasis is on what changed since the previous position, including the information supplied by empty marks.
3. Choose the next useful line
Combine the four techniques without being told which one to use next. Check each conclusion against the displayed clues and leave unresolved squares open rather than completing an imagined picture.
What the explanations can establish
A line deduction uses that line's clues and established marks. Unknown squares may be settled by crossing clues even when the line alone cannot decide them. No surviving patterns means the present constraints conflict; it does not automatically identify the first wrong move. A unique solution is not a promise that the four introductory techniques will finish every board.
Hints in this study area use the current marks. In Nonograms, Tents and Bridges, deductions assume earlier marks are correct; a local conflict stops the suggested step, but absence of a warning does not certify every mark. Minefield flags are never used as evidence. Cross Lights tests complete first-row choices and verifies the resulting plan.
Read a complete illustrated solve
Follow the original board walkthrough, with before-and-after diagrams and a final rule check. It is available without JavaScript.
Keyboard: Tab to controls and press Enter or Space. Board state saves locally; no account is needed.
DECISION LAB
One clue set, 120 different pictures
Investigate whether a plausible picture is actually determined by its clues. A complete solution can be valid without being the only solution.
Test your prediction and follow the evidence →