Hmm, does the door 'swing' open or retract up or to a side?

If its a retractor-diir, make a decal/sprite on the floor that looks like a shadow.
Then as the door retracts, contract the shadow's scale_x to scale_y by a matching amount.

EG: then the door is 50% closed, the shadow sprite is at scale_x=0.5
Get what I mean?


If its a swing-door, I dont have any ideas at this point.