Wanrumuwandoa

Wanrumuwandoa ("One Room One Door") is a logic puzzle published by Nikoli. A rectangular or square grid is divided into regions ("rooms"). A region may contain a cell with a number. The goal is to blacken some cells of a grid according to the following rules:

• A cell with a number indicates how many cells in the region must be blackened. In regions without a number any amount of cells may be blackened.
• Blackened cells should not share an edge.
• All the white cells must be connected inside a region (it's possible for a region to have no white cells).
• If two white cells are orthogonally adjacent across a region boundary, they form a "door". There can be no more than one door between any two regions.
• All the white cells must form an orthogonally continuous area.

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