When I was a boy I found an app on MacOS 8 called Graphical Calculator. You could type in nonsensical maths like 'sin(x+tan(y))' and it would draw beautiful pictures.
20 years later I get the same kick out of GL shaders. I built this website to play with them.
You probably know https://www.shadertoy.com/ already, but if not, prepare to have your mind blown. Many shaders there use Signed Distance Fields to draw intricate 3D geometry within the fragment shader. If you find that interesting, check out Inigo Quilez's excellent tutorial series: https://iquilezles.org/articles/raymarchingdf/
20 years later I get the same kick out of GL shaders. I built this website to play with them.
https://tinyshader.com/rq