Just press the green flag.
I was bored so I spent about two hours porting the core parts of my raymarcher (written in a language that is actually meant for this, GLSL), into Scratch. It doesn't have a lot of important features (like rotation), and it's very slow, but it has some basic lighting and the camera can move around. You can mess around with some variables in the code - the most interesting will be the camera's location in the when flag clicked script, and the SDF and colour functions (you must change both of these to add new objects, at least if you want colouring to be correct).
