A free program for Android, by Good Weather Corp.
Set Brightness Per App is an application that allows you to control the brightness of any application. It's a very simple and easy-to-use application, and it has an interface that allows you to set one single value, two different brightness levels for day and night, an auto brightness with an adjustment level, or even create your own auto-brightness service that uses whatever values you want.
It also supports audio levels, play music, set the display's sleep time, and turn on or off wifi and bluetooth for each app.
It has a simple and clean design and no ads.