Thanks for the feedback!
We went with the idea of a game with only "one color". Just like Black elements could only be seen with a Blue background, the blue player could only be seen with a black background. As you see it doesn't work like actual light which frustrates a lot of people, we'll probably add more visual feedbacks to make it feel more pleasant.
In addition to the one color, the game plays with only one screen where you must survive alone.