The menu should act as a simple pop up dialog with a few buttons etc.
This view should be invoked by pressing new Gear icon next to the brightness control widget.

For now it may contain a link to this GitHub repository and current application version string but in the future it will be a place for configuring rest of the features.

Introduce translations for static strings in the application.

There should be a color picker in the application options which enables the user to change the background color of the app.

The UI should smoothly disappear when screen isn't touch for a moment and bring itself back again when touched. This will ensure that we are using max area of the screen for a flashlight and the screen will be simply more clear.

On the same row as options button there should be a reset button which will change the screen brightness to 100% and reset its color if it was changed before. This will also introduce some more balance to the interface since adding the option's Gear button.

Hey,

I've just tested your app and it looks great on my Android. Do you plan to release prebuild version ? If you are interested I can list it on my open source repo at https://openapk.net/ so other people can try it !

There should be a slider for changing the screen brightness.

Things such a current screen brightness should be saved to the application's preferences or something similar and loaded on the next launch of the application.

In the options should be an option to lock the state of the screen's flashlight. The lock will permanently enable the flashlight and disable the switch button. By enabling this feature user will no more switching their flashlight by an accident.