CheX Challenger app for iPhone and iPad

CheX was invented by George Robertson, a 97 year old computer enthusiast. He developed a paper based version of the game over a two year period with the assistance of his son Glenn. George then developed an electronic version of the game on his desktop computer. It was later adapted for iOS devices by Laurie Davis.

CheX is a two person board game that involves strategically placing numbered tokens on a board. Like Sudoku, a number can only appear once in any row or column. Points are collected whenever a token is played, however points are only awarded when a row or column is completed by either player. All points collected by both players in a row or column containing a blocked cell are lost for scoring purposes.

The rules are simple but the strategies can become quite complex.

The basic game is available for free, but there are two additional capabilities available with an in-app purchase. You can purchase the ability to play against an automated opponent. You can also purchase the ability to play against an opponent using Game Center (iOS 5 or later).