In this intro and in almost every modern 4kB intro, the graphics are made in a shader. To play with shaders, I'd recommend you to look at https://www.shadertoy.

In this intro and in almost every modern 4kB intro, the graphics are made in a shader. To play with shaders, I'd recommend you to look at https://www.shadertoy.com/ https://www.shadertoy.com/. Check also Inigo Quilez's website (https://www.iquilezles.org/ https://www.iquilezles.org/), it has a lot of fascinating content.