Otto Janko claims to have developed this puzzle first.
Puzzle and Goal
An unsolved puzzle consists of a square grid with some number clues in it.
The goal is to place numbers in the blank cells to satisfy the clues.
The solved grid must satisfy the following conditions:
Each rank will have the same number of blank cells. No number appears twice in the same rank in the solution; use the numbers from 1 to N, where N is the number of blank cells in each rank.
The clues represent the total of the neighbors of the clue cells (not including other clues).