Flat Shading on cubes?

In the NeoSpark314's implementation the cubes look... "volumetric"? As in "cubes have depth and shadows". Sadly, the NeoSpark314's version fails to load on my Quest 3s (black screen), so I can't take my own pictures, but here are some from his repo:   Meanwhile, this is what cubes look like in this port:  Even the itch.io page portrays cubes al flat and lifeless:  Here's a picture from my Quest 3s:  Is there a way to make cubes feel "3d" again?