Animation and the overflow property
We have two embedded svgs with moving circle. One orange moves from
left to right, one blue from right to left. Each of them is in its own
svg. Because the border of both is in the middle (marked with a thin
line), both vanish in the middle like in an annihilation.
This is for overflow hidden. In a second turn after 10s both overflows are
set to visible. The circles will continue their motion in the box of
the other circle and will not vanish.