To you who wants to use smart phones by all means in a dark environment such as in the midnight when going out in the bedroom in the futon.

You can make the brightness of the screen much darker than the minimum setting of the system.
Use it when operating smartphones in a dark environment.

Caution:Please do not use in conjunction with an application or screen filter application which makes other screen dark.
When used in combination the screen may become completely black which makes it impossible to operate.