Some Bulletpoints:
- A kind of introduction and explaining the core game loop. This can be in-universe, very weird and deliberately unsettling / confusing
- Player has to be aware of the rules of this place, and needs to be eased into them
- Animated anomalies, increasingly bizarre changes to the environment
- Some visible indication of progress (A voice praises you, or some writing on the wall "Nice! Well done!" etc.)
- Access to other levels has to result from actions in these maps/ levels. Maybe things like: Placing the chair upstairs to trigger a certain progress in the game, or opening a door etc.
- Generally more things to interact with, switches, flashlights, weird objects etc.
- Feeling that something hostile or otherwise intelligent is watching and testing you
- Some lore for the place, what is it, why am I here etc.