Mochikoro

Rules

Shade some empty cells so that the remaining white cells form rectangles, including squares. Two white rectangles can only touch diagonally. All rectangles must be connected through their corners. Every cell with a number in it must be part of a rectangle of the same size. Every rectangle must contain at most one number. No 2×2 group of cells can be entirely shaded.

(Rules and example from WPC 2017 IB)

History of the puzzle

First appeared on Nikoli volume 100 (2002). Invented by けんじゃ (Kenja, lit. "sage"). Mochikoro comes from "mochi" + "colony" in Japanese.

Appearances in the past WPCs

• WPC 2017/Round 7 by Prasanna Seshadri