- ➊ Blacken some cells of the diagram [paper] resp. color the gray cells of the diagram black or white [interactively].
- ➋ The numbers on the left and top edges of the diagram indicate the length of the longest sequence of consecutive black cells in the corresponding row or column.
- ➌ The numbers on the right and bottom edges of the diagram indicate the length of the longest sequence of consecutive white cells in the respective row or column.