Brain Tuner - Give your brain a tune-up

BrainTuner is a free app for iPhone which tests how fast you are in counting. The interface is really easy to navigate. Firstly you select the mode. It depends on how many problems you want to solve, but you have to choose among 20/50/100 problems. Every mode has its own "best time". After you start the game, you have to decide whether the equations are right or wrong. It's quite addictive after a while.

My personal best time for the 20 problems is 9.36 seconds, I don't know if it's good or bad, you can let me know in the comments.