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 ti