Islands

See Nurikabe for a different puzzle also sometimes called "Islands".

Rules

Shade in a polyomino in each thickly outlined region such that no two polymoinoes touch each other by a side, no two regions sharing an edge contain polyominoes of the same size, and a numbered region contains a polyomino of that size.

(Rules and example from WPC 2017 IB)

History of the puzzle

First appeared on Nikoli volume 117 (2006). Invented by 木兄 (Mokuani). Originally named 島国 (Shimaguni, lit. "Island country").

Appearances in the past WPCs

• WPC 2017/Round 7 by Prasanna Seshadri
• WPC 2017/Round 12 by Ashish Kumar