A very simple people, it is the volume setting app.
I can set the brightness of the backlight, various volume, manner mode.
There is also a simple widget.

※ This is the paid versions. Free version of the banner with, please see below.
(Difference between the free version and paid versions is only the presence or absence of advertising banner)
https://play.google.com/store/apps/details?id=com.kitalab.simplevolumefree


※ brightness display of the widget, is only reflected immediately at the time of the setting in this app.
※ Please do not install and use at the same time paid versions and free version.