Heyawake

Rules

Shade some cells black so that all remaining cells are connected orthogonally and no two black cells share an edge. The grid is divided into regions by thick borders; a number in a region indicates exactly how many cells in that region must be shaded black. Every "word" in the grid (a group of unblackened cells connected to each other either only horizontally or only vertically) may not cross more than one thick border.

(Rules and example from PGP IB)

Rule Variations

• In most Heyawakes, every regions are rectangles. When the puzzle contains non-rectangular regions, it is called Heyawacky. This name, now commonly used, was an idea of Thomas Snyder (USA) in 2009.[1]
• In Heyawacky, the last rule is sometime altered to "Every 'word' in the grid may not lay in three different regions." The two rules are equivalent when all regions are rectangular, but are not always so in Heyawacky.

History of the puzzle

First appeared on Nikoli volume 39 (1992). Invented by Hiroyuki Fukushima. へやわけ ("Heyawake") means "dividing rooms."

Variants

Akichiwake

Introduced by Prasanna Seshadri (India). First appeared on Parallel Universe II – Inversion Invasion, held in April 2014. [2] Akichi (空地) is Japanese for "vacant land".

Shade some cells. Shaded cells can’t touch each other by a side. The remaining white area has to be connected. The white area can't span over two consecutive thick boundaries in a single row or column. The numbers indicate the maximum possible continuous white area within a region. There need not be an area equal to this value; the only restriction is there can be no continuous area larger than the value.

(Rules and example from WPC 2017 IB)