Container

Container are useful for constraining a sticky element. Setting a container is done by adding a container attribute the id of an element. It simply checks the bounding box of that container element. If the container's bounding box is not big enough to contain the sticky element it starts to disappear.

I'll be sticky, but only for a short while. Once the grey box in the background disappears if you scroll too far, the sticky element goes with it.
I'm just here to give the sticky elements some space.