How do I tell which Antechamber door opened?

I swear I've read so many tutorials on this but I simply can't tell. I can open a door or two but I can't tell from the animation when the door opens which side of it has opened. Like, I saw a door on the right side of my screen open so I built up to the right side and it was closed and my game ended. I'm really trying to figure this out. Sorry if this is a common question, please forgive.