Use a circle for the ball in Breakout

[alice-i-cecile]

Once #3730 is merged, we should represent the ball as a circle, rather than a square. We can probably stick with the AABB collision though for simplicity.

[rparrett]

I have a feeling that in practice, not doing proper circle-aabb collision would end up looking pretty janky, but I'd personally love to see that if it doesn't complicate the example too much.

[mockersf]

as a side note, this could already be done by using a round image, like https://github.com/bevyengine/bevy/blob/main/assets/branding/icon.png

[alice-i-cecile]

#3730 is merged so this is now quite easy :)

[tkgalk]

I made a PR pretty much exactly the same as the #4682, if there is no answer from the creator of that PR, I can submit mine if you wish.

[alice-i-cecile]

Yes please @galkowskit :) Just link to the other PR and we'll credit you both.

[tkgalk]

#5657

[rparrett]

So the obvious collision "corner case" is this sort of thing:

corner-case-heh.mov

We could

1. Have a circle with slightly wrong collisions
2. Have a square with better collisions
3. Fix the collision code

I have a slight preference for 2 but it seems like fixing the collision code would be sort of involved, so I suppose I don't really mind 1.

[tkgalk]

I think it also touches the physics issue. There is a very rudimentary code for reflections.