Hi gang!
I was testing fullscreen ADT .background options, and found an 'oddness'.
https://www.babylonjs-playground.com/#GL5SIM#3
When using left-mouse-drag of pointer/camera, pointer goes in-active over red buttons. Or maybe I should say... pointer gets "commandeered". 
(LMB-drag the camera, making pointer cross the red buttons)
Perhaps GUI buttons should NOT check for onMouseOver IF a mouse button is already depressed (drag in-progress).
Seems ESPECIALLY important when ADT is set !isForeground (set as backgrounded). But issue is seen in foreground mode, too. [link]
Really, though, whether ADT isForeground or not, I think nothing should interrupt a drag in-progress.
During a drag, CSS cursor MIGHT be set as "grabbing hand", perhaps dragging a mesh. We don't want the drag interrupted when crossing ADT controls, right?
Anyway... just checking. Everything might be fine. Thx for verification/thoughts.