Use the row/column number clues to figure out which cells should be filled — each number is a run of consecutive filled cells, in order, with at least one gap between runs. Fill mode: click/tap to fill a cell (click again to clear). Mark mode: click/tap to place an ✖ on cells you know are empty (helps you track your logic). Right-click (or long-press on touch) toggles a quick ✖. Complete the picture to win — "New Puzzle" cycles through 5×5, 10×10 and 15×15 grids.