How do I use a ring for particle bounds?

Hello! I'm trying to simulate a molecular movement. the more heat the greater the movement. For now I got the basics covered. I put approx. 10 particles (sprites) on my canvas, and with physics have them bounce around 4 invisible rectangular sprites forming a box.

What I am looking to achieve is that the particles would be "trapped" inside a circle and have the circle expand and contract to give the particles more space to travel.

Is this something doable. I am assuming it would have something to do with the collision shape, but not sure how.

thx!

Marc.

Inner collisions are not the easiest thing to solve but here is a very simple solution. Use multiple collision walls around the outside to collide off of. Take a look:

drive.google.com/file/d/1hzYGcbF0W3DEtcVQ8K3na8FG7NeHQB7K/view

Yeap, like you said, it's a working solution, but not the best, especially that I need the collision boxes to expand and retract.

Thx! for the reply.

The boundary objects can be scaled to create the expand and retract effect. Check out the changes to the project and you can see it working with a sine wave affecting the size.

Very cool!!! thank you so much!

cheers!

Marc.

Thanks George, very nice result (yes indeed it's what I was looking for) ... I got it to work with InDRekt's solution.

I will study yours, because I'm not too good with sin and cos (Physics weren't mandatory at school LOL) so i missed on some essential game physics.

cheers!

Marc.