Don't open the door

Open...

The sign.

Either that, or look around the room and see what else is in here. One of the two.

You look at the sign but fail to understand how to open it, because it's just a piece of paper taped to the door, so you decide to look around you instead.

The room is completely empty. There is nothing here beside you, the door, and four perfectly white walls. When you look up you see a couple fluorescent lamps that are too high for you to reach. You can't seem to find the light switch anywhere though.