Ok here is my first improvement: I know it's quite simple but I'm a 3d artist not a programmer!

Define this in the beginning of c_functions.c

var camera_distance = 200;

And this in the while loop of handle_input_startup

camera_distance -= mickey.z * time_step;
camera_distance = clamp(camera_distance, 300, 1000);



Now you can zoom in and out with your mouse wheel!