The app uses a flash to test your reflexes. After the flash, quickly press the "REGULAR" button (measures reflexes when the flash is regularly fired) or the "NONREGULAR" button (measures reflexes when the flash is irregularly fired). The test can be performed using a bounce flash or a close flash (illuminating a nearby object). The test is best performed in the evening or in a dark room. The app is currently in the testing phase. It may work on some smartphones. The time between flashes is 3 seconds (REGULAR).