GridX X for Mac

From Blufire Software:

GridX is a small, simple mental math game. The object is to fill in numbered squares on the grid, before the time limit runs out. The time limit can be adjusted, and can be set for either a single round (count down the time for one square on the grid), or for the entire game (where you must fill in all the squares before the set time runs out). This can be difficult, but there is a high scores list, so you'll still get your glory. :) Go ahead and try out this little bit of freeware!