They combine the people that sign up so you can just sign up yourself. I think it's 8 people per session.
More people, faster puzzles are solved. Most rooms maximum is 10 person.
At least two, four is about optimal for the easier rooms, some might be better with more
We did four. I feel like you could enjoy with two or three.
The maximum amount of people allowed at once is 10. I don't believe there is a minimum, you simply run the risk of another party signing up and being in the same room as you.
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