By the way, I think this one is in the mod but only with green feathers from the wings to the wings; there is another version of this bird with yellow plumage. https://en.wikipedia.org/wiki/Scarlet_macaw   I don't know if @Lopess can confirm.

Hi 0AD community, I'm making a game engine under Creative Commons. With permission, I'd like to use graphics from 0AD. My game uses 2D sprite sheets. I'm no artist, but I'm willing to pay for a detailed tutorial on how to convert from 3D assets to 2D sprite sheets. I'd also like to be able to export the shadows cast by the the objects onto the ground plane. Any takers? Boston https://bbrooks193.blogspot.com/2021/12/maths-game.html

I thought the defender is that one who's movement gets influenced by the attacker. So when two units collide they are both on the same time attacker and defender, depending on which movement is calculated.

I don't know if they'll be in any mod.  

Since those wouldn't really solve sliding against a wall, what about ellipses? The equation is not that much more complicated than for circles (which are a particular case of them), but maybe many things have to be changed...