Numbrix, developed by Marilyn vos Savant, is a logic-based numerical puzzle challenge in the vein of Sudoku. The game premiered on July 13, 2008, in vos Savant's syndicated column, "Ask Marilyn," which appears in the Sunday newspaper magazine, Parade. The puzzles may be completed online or printed for offline play.
Numbrix, featuring several levels of difficulty, is configured on either 7x7 or 8x8 grids and challenges players to fit a certain set of numbers, 1 through 64 or 1 through 81, within the confines of the grid. Numbers must be entered in sequence, and the player may only move up, down, right or left; diagonal moves are not permitted. If the puzzle is finished correctly, a line traveling from the first number to the last does not cross itself.