As a lot of phones have AMOLED display whenever a desired notification comes the app brings in a black screen with edge lighting. To use it: 1. Disable any battery optimisation for the app. 2. Give notification access permission. 3 Select apps you want notifications for, by choosing a color Thats it😇. For MIUI 11 devices make sure that AutoStart is enabled in App Info. Also check "Show on lock screen" permission in other settings. Settings image: https://drive.google.com/folderview?id=1yxrLd