This app shows an overlay (always on top window) showing a color chosen by you which dims the screen or filters its colors. This may help a night to relax your eyes as most phones screens are to bright and could permantly damage your eyes when staring at it to long while it's dark around you.
Additionally screens with a tint of blue have been associated with insomnia when stared at before going to sleep. By selecting a red or yellow filter some of the blue colors emitted by your device aren't shown anymore which might prevent this (No scientific confirmation on the effect of this app)

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