You can select the set 3 brightness and AUTO from the notification area.
Since you can select from the notification area, you can select the screen brightness without dropping the running application.
When you tap the icon in the notification area, the setting screen is displayed, so you can easily change the brightness.
Brightness setting 1 has a filter to make the brightness even darker, so even the lowest brightness can be used even if you feel dazzling.

[About authority]
"WRITE_SETTINGS (change system settings)" is the authority required to change the screen brightness.
"SYSTEM_ALERT_WINDOW (displayed on top of other apps)" is the required permission when the filter function to further darken the brightness is enabled.
"RECEIVE_BOOT_COMPLETED" is the authority required to automatically start the app when the terminal is restarted.