MacMost makes great games.  The website instructions say the game: is to select numbers that add up to the goal. For instance, to add up to 17, you may click on a 5, 8 and 4. When you reach the goal, a number goal is generated. The game ends when a goal is generated that can not be reached with the numbers left on the grid. Your score is based on how fast you are able to reach the goals, and how many numbers you used to get to the goal -- the more numbers the better.

If you like math and games give this a shot.  You might also like a game called 'A Racing Game.'