Heyawake: walls and white paths
A white line may cross only one wall, and the white cells must stay in one piece. Between them these two rules shade most of the grid.
How it works
The three-room rule: a straight line of white cells may cross at most one wall. So any straight run that goes from one room, through the whole width of the next, into a third must have a shaded cell. When all but one of its cells are white, shade the last.
Stay connected: all the white cells join into one piece. If shading a cell would cut some white cells off from the rest, that cell is white.
When neither rule moves, try it and see: suppose a cell is white, follow the rules, and if something breaks, the cell is shaded.
Spotting three-room lines
Look along each row and column for a room that is narrow in that direction. The cells on either side of it, plus the narrow room’s cells in that line, form a three-room line.
A room one cell wide gives the shortest lines: just three cells. Once two of them are white, the third is shaded.
Worth memorizing
A white line crosses at most one wall.
Never wall white cells in.
If shading cuts them off, the cell is white.
Stuck? Suppose a cell is white.
If a rule breaks, it is shaded.
Practice
0 of 4 rightWhat is the ringed cell?
What is the ringed cell?
At the start, using rules 1 to 3, what is the ringed cell?
Try it and see: what is the ringed cell?