How I rebuilt "Flying Toasters" using only CSS animations
bryanbraun.com
bryanbraun.com
Seems like the toasters don't overlap each other, but they do overlap the toast (eg, at 0:08).
Anyway, very cool CSS creation.
I don't think that this could be recreated in CSS only, you need to do at least some calculations and conditional execution for this. This is probably the max you can get with CSS only. Congrats.
One thing that could be done with this is to make an Android 'daydream' screensaver. That would be 'useful'!
How would animating the z-index cause the sprite to move from the top right to the bottom left? Z-index controls what draws in front of what, not spatial position.