It is a simple blue light blocking app.

[What is Blue Light?]
It refers to light between 380 and 500 nm where the blue light is strongest in the visible light wavelength. This light is harmful light and exposed to our eyes for a long time will interfere with clear vision and it will have bad effects on human body such as eye dryness eye fatigue insomnia shoulder stiffness back pain. Nowadays when computers smart phones and LED displays are spreading they are exposed to light all the time and it causes unstable cytoplasmic aging and biorhythms without us knowing.

[Influence of blue light on human body]
1. Dry eye and promote eye fatigue
2. Insomnia induced by inhibition of melatonin formation
3. Tension (vital alarm) body temperature rise pulse rate increase
4. Hypersensitivity stimulation in case of photosensitivity
5. Promoting cytotoxic aging

[Features]
1. Change brightness and transparency
2. Select color
3. Simple operation through icons in the status window
4. Low battery consumption

[ Accessibility Service ]
In order to filter also your notifications and lock screen the app may ask for enabling BlueLight Filter Accessibility Service. The app uses this service only to better filter your screen and does not collect any personal information.

[ Referece site ]
https://dontkillmyapp.com/
This website that provides information in order for the app to work well. (English)