https://www.cross-plus-a.com/help.htm

Kabingurodo

Kabingurodo ("Curving Road") is a logic puzzle invented by Naoki Inaba (Japan). It consists of a grid, with circles in some cells. The aim is to blacken some cells of a grid according to the following rules:

• Cells with circles are always white.
• Black cells must not be orthogonally connected.
• All the white cells must form an orthogonally continuous area.
• Each path from one circle to another circle on white cells must turn at least two times.

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