A little Linux demoscene starter application I've written (C + GLSL):
A C demo template. It makes an executable that's 7kb and can be shared to other systems.
I've use my superformula SDF code from years on back.
Uses _start syscalls and eschews the standard library in order to be that size.
It also only uses libGL and libX11, that's it.
That said: I have no idea how people manage to make 4k demos, ha.