Depends on the game. The Hex Room is designed best for 6 people to get the full experience but I think they made it so 5 can do it. Their Psychward room requires 5. And they Fun House room can be done with like 4 I think.
It varies depending on the room, but some puzzles are more difficult with fewer people. Funhouse can take the fewest players at 4.
We had 4 and had our own room.
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