I've been experimenting with making 3D objects on Scratch. In this project, I experimented with making cubes. Click and drag or use arrow keys to rotate the cubes. You can press space to show a bunch of variables used in the calculations.
This 3D engine tutorial helped me a lot: https://scratch.mit.edu/projects/441460754/ Check it out too, it gets more into detail of how this works. The only unfortunate thing is that it doesn't go over how to fill the cubes with color. I tried to figure it out myself and put some comments in the project to explain what I did. It isn't perfect though. :( Enjoy!