When commencing a level, you have various digits shown on top of the columns and to the left of the rows; alongside a series of corresponding red squares on the bottom columns and to the right of the rows. The numbers correspond to the amount of coloured boxes for that given column or row. When filled in correctly, the corresponding light will turn green. You can either choose to fill in a square with the pencil, or tabulate to a blankspace by tapping the pencil icon (similarly to leaving flags in minesweeper). Note that you do not actually colour the painting in; you only see the colours when you solve the puzzle. Certain rows and columns may have a single number such as [3]. However others may have something like [1][1]. The latter indicates that there should be 2 filled boxes in a given row or column, and also that the 2 filled boxes cannot be next to each other in that row or column.