Also known as Picross. Use the numbers beside each row and above each column — how many cells in a row are filled, in order — to work out exactly which cells to fill and reveal the hidden picture.
Rules
Left-click a cell to fill it in; left-click again to clear it.
Right-click a cell to mark it as definitely empty, to help track your deductions; right-click again to clear the mark.
Each clue number is a run of that many consecutive filled cells, in the order shown, with at least one gap between runs.
The picture is complete the instant every filled cell matches the hidden solution.
Tips
Start with the longest runs in the smallest grid — a run close to the row or column's full length leaves very little room to move, so many of its cells are forced from the very first clue.