Lego Menger Sponge (Shader)

This shader is one of my first procedural generated effects by only use code (no models, meshes and textures).

Techniques:
* Ray Marching & SDF (signed distance field)
* Menger Sponge
* Soft Shadows
* AO
* Reflections by using smoothstep
* Color Shifting

Shadertoy: https://www.shadertoy.com/view/ttXSzB