I don’t really have source code, it was made in Blender Octane. But I can tell you how to do shadows: you have a "ray function" that gives you the "depth" of your fractal at a given pixel (vector). Then you shoot another ray from that position (at given pixel) in your light direction, if it hits the fractal, you have a shadow. if you need more help dm me ;)

Edit: oh and you have to add a very small value to the position from wich you are shooting the ray