A free app for Android, by Nu-Kob.

Screen Dimmer is an easy-to-use and stable app. It can dim the brightness of your Android screen from 0% to 100%. You can also set the dimmer to a fixed level or auto-start after reboot.

When you open the app, you will see a notification bar with a slider. You can drag the slider to change the brightness. The dimmer will auto-start after reboot, so you don’t have to worry about turning it on and off manually.

This application has been tested and looks good on a variety of devices. You can open the application by tapping the notification bar.