Ripple Effect is popular logic puzzle game in Japan.
The solver must place one positive integer into each cell of the grid according to these rules:
Every room must contain the consecutive integers from 1 to the quantity of cells in that room inclusive.
If two identical numbers appear in the same row or column, at least that many cells with other numbers must separate them. For example, two cells both containing 1 may not be orthogonally adjacent, but must have at least one cell between them with a different number. Two cells marked 3 in the same row or column must have at least three cells with other numbers between them in that row or column, and so on.