Heyawake: rooms and counts
A shaded cell makes its neighbours white. A room with its count is finished, and a room that needs every open cell gets them all. When a room is tight, try each way to fill it.
How it works
A heyawake room number counts its shaded cells. These moves read the numbers, room by room.
Shaded neighbours: shaded cells never touch by an edge, so the open cells beside one are white.
Room count: a room that already has its count is finished, so its other cells are white. A room that needs as many shaded cells as it has open cells shades them all.
Room patterns: when a room is small, try every way to place its shaded cells. A room pattern that makes two shaded cells touch, or walls white cells in, is out. Where all the patterns left agree, the cell is settled.
Counting room
A room can hold at most about half its cells shaded, because shaded cells can’t touch. A 3 in a room of five cells in a line has one pattern: shade cells one, three and five.
Cells outside the room matter too. A cell beside a shaded cell in the next room is white, which can leave a room with fewer places than it needs.
Worth memorizing
Next to shaded means white.
A room with its count is finished.
Its other cells are white.
A 2 in a line of three shades both ends.
The same idea works for any tight room: try each pattern.
Practice
0 of 4 rightWhat is the ringed cell?
Using only shaded neighbours and room counts, what is the ringed cell?
What is the ringed cell?
What is the ringed cell?