Kurotto
Background
Kurotto first appears in Puzzle Communication Nikoli #138 (March 2012).
Puzzle and Goal
An unsolved puzzle consists of a rectangular grid; some cells contain numbers.
The goal is to color some of the squares black.
Rules
The solved grid must satisfy the following conditions:
Numbers indicate the total number of black cells in regions orthogonally neighboring the clue.
No square with a number can be blackened.