Concentrate is based around a training program for pilots, giving the player a chance to measure their skills and improve with each workout. Gameplay is easy to understand; just find all the numbers in an alternating fashion (black and red) in groups depending on play level. You can see your progress as awesome little graphs, showing you how much you've improved. The player can also measure their personal success against the world through Swarm.
Concentrate is a fantastic free way to quickly flex the mind muscle. Who couldn't use a brainpower boost?