Attention! Probably this application works properly on high performance devices only, with FPS up to 120 frames per second.

This is an implementation of a psychophysiological test, namely critical flicker fusion.
Measure how tired you are. All other things being equal (brightness, characteristics of flashes), the critical fusion frequency is the lower, the higher the level of fatigue.
The essence of the test is to determine the minimum frequency at which light flashes merge into continuous light.
The application can work in two modes: automatic and manual. In the automatic mode, the frequency increases and decreases automatically at a standard speed of 0.5 Hz. In the manual mode, the frequency can be changed with the horizontal swip or with the seek bar. The color of the light flashes can be set differently, white, red, green or blue.
You can change size of the light flicking square. Just swipe horyzontally at the level of the square.
The brightness of light flashes is of great importance. To ensure comparability of results, it must be constant. To do this, it is recommended to disable the adaptive brightness control mode in your device and set the brightness to maximum. It's also a good idea to measure the brightness with a light meter.
You can also use this application as a some sort of flashing light mind machine.
Internet permission needs only for access to admob advertising.