Chenburo

Chenburo ("Chain Block") is a logic puzzle published by Nikoli. A grid contains numbers or question marks in some cells. The aim is to blacken some cells of a grid according to the following rules:

• The black cells form blocks. No blocks touch each other horizontally or vertically (only diagonally).
• A number represents the amount of black cells in the block. Question marks can be used instead of clue numbers. Each question mark can represent any nonzero integer.
• Each block contains exactly one number or a question mark.
• All blocks form "chains". A chain is a group of two or more blocks, connected through their corners.
• Two blocks belonging to the same chain may not have the same shape and size, counting rotations and reflections as the same.

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