Rukkuea ("Look-Air") is a logic puzzle invented by Nikoli. The puzzle consists of a rectangular or square grid with numbers in some cells. It is necessary to blacken some cells according to the following rules:
- Black cells form an area of square shape.
- No black areas touch each other horizontally or vertically (only diagonally).
- Black areas of the same size must not "see" each other: horizontal or vertical lines between two black areas must contain at least one black area of other size.
- Each number shows how many of the five cells (the one with the number plus the four orthogonally neighboring cells) should be blacken.
Cross+A can solve puzzles from 3 x 3 to 30 x 30.