The origin of this puzzle is not known; Janko.at first found it in Puzzle Fountain (Alberto Fabris).
Puzzle and Goal
An unsolved puzzle consists of a square grid with numbers to the top and side.
The goal is to place exactly two black squares in each rank.
The solved grid must satisfy the following conditions:
Clues indicate how many white cells are between the two black cells in that rank.
Black cells cannot appear in diagonally adjacent cells.