Transforms, Transitions, and Containing blocks and Viewports

This is a fixed-positioned element. Its containing block defaults to the root element but switches to its containing div when that element is transformed by hovering.

This is a normal-flow element. Hover the mouse pointer over the containing div (the green-bordered box surrounding this one) to see the fixed-positioned element shift.

This is an absolutely positioned element. Its containing block defaults to the root element but switches to its containing div when that element is transformed by hovering.

This is a normal-flow element. Hover the mouse pointer over the containing div (the green-bordered box surrounding this one) to see the absolutely positioned element shift.

This div exists to make the page tall enough to force scrolling. That's it.