This demo tests drag operations where the reference element (what you click/drag) is in a different positioning context from the element (what actually moves).
Test Scenarios:
Click and drag the orange REF element to move the green ELEMENT. Both elements are in the document (same scroll container) but have different positioned parents.
Click and drag the orange REF element (in scroll container) to move the green ELEMENT (in document). Tests cross-coordinate system drag operation.