Algodoo

Nice presentation and code.

“Sound waves? Delightful things—much slower than the ones I’m famous for, but at least they don’t require a spark gap to enjoy a good opera.”

You could also use a piston pump as a power source and a check valve as the rectifier.

NIce.

Q: Who are some of those guys?
A: surfingscientist

This image features popular YouTubers (from left to right) Marcus Butler, Joe Sugg, Zoe Sugg (Zoella), and Alfie Deyes. This specific photo was taken during a collaboration or social gathering in the mid-2010s, a time when these creators were at the peak of their YouTube fame.

I assume the others are more readily recognizable.

I figured as much, but inquiring minds want to know.
Besides those people went thru plastic surgery just for your Algodoo scene. The least you could do is mention their names.

Thanks.

I like the concept, functionality, and presentation, but what's up with "sim.borders"? I don't believe Algodoo supports a "sim.borders" method.

Yes, works as intended. Congratulations on fixing the issue. Creating new application variables is not good practice, better to use "Scene.my." variables.

I was thinking the same thing when I made the scene. Here's one way of looking at it:
Imagine you start with a straight rack and a 12‑tooth pinion gear.
Make the rack exactly twice the circumference of the pinion. If you roll the pinion along the rack from left to right, the pinion will make two full rotations by the time it reaches the end.

At that final position, freeze the pinion relative to the rack—as if you welded them together.
Now hold the left end of the rack fixed, and bend the rack into a circle so its ends meet. You can bend it so the teeth face outward (forming an external gear) or inward (forming an internal gear).

When the rack is bent into a circle, the gear that was “frozen” at the end of the rack is forced to undergo one additional rotation (for an external gear) or one fewer rotation (for an internal gear) in order to close the loop smoothly.

AI offers this simpler explanation:
Think of a planet gear rolling around a sun gear.

When a gear rolls around the outside of another gear (external mesh), it not only turns because of the tooth engagement — it also turns once more because it is physically walking around a circle.

When a gear rolls inside another gear (internal mesh), the walking direction is reversed, so it effectively turns one less time.

Everything works well except for the number guesser getting stuck in its package. The number guesser itself works OK.

You could disable collisions on the handle.

Very nice.