Dynamic Machines is a render challenge I participated in when I was starting out learning blender. The goal was to make a tiny section of a marble machine, so that all the submissions could be combined at the end to make one huge marble journey. Because everything had to lock together so smoothly, the criteria for the video were very specific. I had to get the marble in and out of the box at a specified frame, which was quite tough to line up when I was doing physics simulations and moving objects. But it was a lot of fun working within the confines of the challenge, and I actually ended up making it in the top 100 out of almost 2000 submissions!
Videos
You can watch the creators of the challenge react to my marble machine here:
And here it is in all it's glory, working together in tandem with all other marble machines: