Add It Up is a time driven game. Choose a combination of numbered tiles by clicking on them to add up to the target number, which is located in the upper right corner of the screen. Each numbered tile has a points value, which you earn when you choose that tile to add up to the target number. The more tiles you choose to get to the target, the more points you earn for that turn. There is a timer located in the bottom right of the screen. Earn time bonus points for choosing your combinations quickly.
You are awarded extra points for clearing all of the numbered tiles, but 500 points are subtracted for every remaining numbered tile left on the board at the end of the game. The game ends when there are no more moves to make or all numbered tiles have been chosen.