Wikipedia
Navigrid
Navigrid is a logic-based number-placement puzzle. The puzzler is provided with a set of movements which must be used to move between the numbers 1 to 9 in order starting with the number 1. A solved grid will contain each of the numbers 1 to 9. The puzzle setter provides a partially completed grid.
The puzzle was invented by an English puzzle enthusiast, Laurence May, in 2006 and was first published by BBC MindGames Magazine where it appeared in all 9 issues. It is produced by Vexus Puzzle Design and is currently represented by Puzzler Media. The puzzle appears along with Sudoku and Kakuro in their "Kakuro" magazine.