Rules - Room and Reason

Room and Reason was invented by the Japanese puzzle company Nikoli.  The name is from mathgrant.

1. Make each cell white or black.

2. The grid is divided into rectangular "rooms".  Rooms with numbers in their corners must have that number of black cells in them.  Rooms without numbers may have any number of black cells in them.

3. White cells may not go through more than two rooms in an uninterrupted horizontal or vertical line.

4. No two black cells may share an edge.

5. All white cells must be connected to each other through their edges.