I also prefer hight and smooth frame rate and super entertainment. And your 3D retro art is great.
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For your levels i see it's blacks screen behind on background Why not putting same color as the level or somewhat darker on background ? Or some very simple painted background :
I agree it's lot more work also !
----------- Yes UNLIT seems to work well with 3DGS, Perhaps i'll make some level editor also in some other easy language.