画面の明るさを最大化し、最小化するための最も簡単なウィジェット：唯一のボタン
The simplest widget to maximize and minimize screen brightness: only one button that
- if brightness is currently at maximum, minimizes it,
- if brightness is not at maximum, maximizes it.
No more, no less.
No settings, no choices, only one small button on your home screen to have the control always ready at hand.
It is a widget, so you install it on the home screen following the usual procedure for Android widget.