This app basically let's you see (numerically) how bright your screen is at any given time. It gives you a number readout that changes when you change the brightness. That's all it does, but it does it well. It is easy to install and the video below shows it.
do not adjust brightness like blind, instead with this tool you can know what is the current level and the level you are sliding to.
like if you were playing a game in night mode map or dark place you can easily and quickly increase brightness and set it back to the level you feel comfortable with it after you finish playing.
Installing this app is just like you installed nothing, it does not consume cpu, ram, battery or anything else.
This app does not run in background, it is lighter than what i can explain.