**Hakyuu** (also known as *"Ripple Effect"*, *"Hakyuu Kouka"*, *"Hakyukoka"*, *"Seismic"*) is a logic puzzle published by Nikoli. The puzzle consists of a rectangular grid of any size divided into polyomino sections called "rooms". Each room must be filled with each of the numbers from 1 to the number of cells in the room. If two identical numbers appear in the same row or column, at least that many cells with other numbers must separate them.

**Cross+A** can solve puzzles from **3 x 3** to **30 x 30**.