Introduction
The app utilizes amazing Xposed framework coded by recognized developer rovo89 which briefly provides interface for injecting code into any app including system services allowing modifications of applications and system services at run-time. One of the biggest advantages of GravityBox is that it is not bound to any specific device. Actually it should run on any device having vanilla Android 7 (ROM close enough to AOSP).
This project wouldn't be possible without rovo's Xposed framework so huge kudos to him.

Support Developer:
https://play.google.com/store/apps/details?id=com.ceco.gravitybox.unlocker