This puzzle appears in Games magazine, among other places.
Puzzle and Goal
An unsolved puzzle consists of a rectangular grid with some blacked-out squares. The other squares each contain two number clues.
The goal is to place a number in each unblackened square.
The solved grid must satisfy the following conditions:
Slide one clue up or down in the same column, through orthogonal cells. Slide the other clue left or right in the same row.
Each number in the solution is the result of slides performed on matching numbers.