The fill light shines from the side and eliminates shadows.
One way to earn Glimmer quickly is to visit each planet and clean out all Region Chests. These are marked on the map as a cross with dot in the middle of it. Each one you open can give you some gear, but after reaching max Power level it's unlikely you'll find much value from that.
Answer: So the easy way to remember the difference between additive and subtractive color mixing is that additive color mixing is what happens when we mix lights of different colors whereas subtractive color mixing occurs when we mix paints or other colored material.
