What I meant is UXML and USS should be possible to declare everything in game, 2D and 3D, not just UI Actually, we could see every visual, audio, bounding or any object that could interact with user as the "UI of the game". The 3D building on the ground that user could touch to invoke popup. A ball that player could drag around. Weapon that user could pick if the character's hand can reach so it would be highlighted. Everything could be considered as UI. Especially in a non realtime game that almost all objects is bound to game state, not physics So it should be possible to serialized every kind of GameObject in addition to VisualElement, into UXML and USS property. And so we could bind a game state that need to sync with UI to visual object in game too. Such as, when we select a character, we want to have some effect on target character along with character UI showing character's information. We could be doing this with UXML and USS, selected character could be defined with USS selector Character:active > selectedEffect and we might set the color display:none or --animator-set-shown:true (custom property that will trigger the animation boolean value) What do you think?