Algodoo

You can make the camera follow the cars automatically if you wanted to. Here's how:

1. Delete that tiny square that currently makes the camera follow it with the arrow keys.

2. Select all of the marbles while they are lined up ready to race. It's Okay to also include those red separators and invisible bars because those things will disappear when the race starts. With the marbles selected, right click on any of those selected marbles, then hover your cursor over "Selection". In the right panel click the checkbox "Follow". Then save the scene. That's it! The camera will now follow ALL of the marbles as a group! No need to puts around with the arrow keys!

Oh, one more note: The user may need to zoom in or out during the race in order to see all the marbles at the same time.