Heyawake is a binary determination puzzle in which the cells in a grid are split into either shaded or unshaded.
The objective is to shade some cells, subject to the following rules:
- Numbers indicate how many shaded cells are in a room.
- Shaded cells must never touch horizontally or vertically.
- Unshaded cells must form one, connected area.
- A straight line of unshaded cells can only connect two rooms, a line of white cells which connects three or more rooms is not allowed.
A standard 10x10 heyawake and its solution.
Unless otherwise indicated, standard heyawake rules apply to all variants.
Heyawaky: A straight line of unshaded cells can only cross over one border at the most, even if it would re-enter a room.
Heyawake Symmetry: Instead of clue numbers, clues indicate whether the pattern of shaded cells has 180° symmetry within a room or not.
Heyawake Twin: Shaded cells share an edge with exactly 1 other shaded cell.