Your screen is too bright. Here's the fix.
Dimmer is designed with one purpose: to make your display darker. The backlight on your phone may work great for outside reading or when the lights are on, but when you're lying in bed at nighttime, the darkest point can still be blinding. And it might even be keeping you up!
With Dimmer installed, you can turn your screen brightness down even further. From 100% to 30%, your normal backlight will control your brightness, and below 30%, Dimmer takes over and lets you virtually dim your screen beyond what your backlight can accomplish.