I love the idea, but it seems like a difficult (but not impossible) limitation. Godot won't make it even with heavy minification of a hello-world, Raylib is more realistic but I think the 3D rendering on its own already puts it above the limit so even untextured 3D is out. So, 2D or write-your-own-engine.
Well, maybe Raylib 3D might work with a static binary via musl, but at that point I'm pretty sure game design and programming would be small steps at that point.