Nonograms

The rules. Each row and each column is annotated with a list of numbers — the lengths of the consecutive runs of filled cells in that row or column, in order. Runs are separated by at least one empty cell. Your job is to figure out which cells are filled and which are empty so that every row's and column's runs match the clues.

Filling and clearing. Click any empty cell to fill it (it turns black); click a filled cell to clear it. Right-click an empty cell to mark it as definitely-empty (a small × appears); right-click an ×-marked cell to clear the mark. Click-and-drag (or touch-drag) across a row or column to paint multiple cells the same way as the start cell.

Mark mode. Press M (or click Mark mode) to flip the primary tap to cycle the ×-mark instead of the fill. Touch-friendly alternative to right-click.

Hint. The Hint button highlights the next cell that line logic forces and explains why — for example, "In row 4, the run of 5 must extend through cells 3 to 7, so cell (4,5) is filled."

Verify. The Verify button compares your current filled and ×-marked cells against the puzzle's unique solution. If you've made a mistake, it shows you which cell is wrong. Use it as a safety net on big grids where small mistakes can cascade. It does not give you the answer to cells you haven't placed.

Sizes. 5×5 plays in a minute or two; 20×20 can take half an hour. Every puzzle at every size is solvable by single-line logic alone — you will never need to guess.

Keyboard shortcuts. M toggles Mark mode. H requests a hint. V verifies. P pauses or resumes the timer. Backspace / Delete clears the cell under the cursor (or the most-recently-edited cell).