The screw acting as a rack? Now there's an interesting thought! I imagine that it would somehow need to be supported along its length to keep it from bowing under compressive load. Also, it would need double the length of the road as it extends.... Wait..... that won't work. Bad idea.
Q: Where is particle?
A: It's located at the opposite edge of the galaxy. What is it doing? I'm glad you asked. It's spinning exactly in synch with its twin, of course!
Your instructions in the scene description are confusing! I tapped the "1" key multiple times and nothing happened. Then after looking into your scene, I saw the script was to recognize the "A" key! Even your comment above is a little confusing. So, here is my suggestion. It is better to word the instructions like this: Tap the "A" key and the cat will turn black.
As long as you use a standard Internet browser, you can edit the existing scene by changing the instructions. But if you use the Algodoo built-in browser, then you cannot edit the scene.
I'm not sure what type of application you had in mind for your User-Made square, but it is extremely rigid. It doesn't have any "squish" to it at all like the spongified square has. I even tried reducing the strength of all the springs, and that did not help the squishiness at all.
No need to get upset about what I said. I was only trying to be helpful. I suggest that you search the Algodoo archives for examples of scenes that are true animations in order to get some ideas for your own scenes. If you would like some help or suggestions with how to animate an image, I would be pleased to help you. I subscribed to this scene, and so I will be alerted whenever you or anyone else leaves a comment.
In case you didn't know this, you can click "subscribe" in each of your scenes so that you will be alerted whenever someone leaves a comment (the words "New Messages" will show up in bold letters near the top of each Algobox page). That way you won't need to check every scene to see if anyone has commented.
Is it normal? Well, if you are asking if that would happen in real life, I would guess probably not, unless the right conditions were met. I believe what's happening is the large circumference, while trying to roll along the darker track, is dragging the smaller circumference along the lighter colored track. If the coefficient of friction is high enough, and the slope of the tracks is small enough, the assembly of circles will get stuck at various places along its path.