This puzzle originated in Japan. Unlike most of the grid-based puzzles, it requires basic math skills.
Puzzle and Goal
An unsolved puzzle consists of a square grid of size <em>n</em>. Along the top and left side (or bottom and right) are the numbers from 1 to <em>n</em> for reference; along the bottom and right (or top and left) are the clues.
The goal is to color in some of the cells to satisfy the clues.
The solved grid must satisfy the following conditions:
The clues at the end of each rank represent the sum of the blackened cells in that rank. For instance, in a 5x5 grid, a clue of 7 could represent 1, 2, 4 or 2, 5.