# These roommates throw strange parties

There are four roommates who throw strange parties. They live in a room with two front doors, and no windows. At the start of a party, the first roommate opens one door, lets the guests in, and closes the door. Then the second roommate forces all of the guests to one end of the room. Then the third roommate snaps his fingers, and the guests spread out in the room again. Finally, the fourth roommate opens the other door, kicks all the guests out, and closes the door. Each roommate spends 25% of the party time doing his part, and just one roommate is active at a time. The party goes smoothly, and the roommates throw more parties just like it, with a new set of guests each time. The room is one of four similar rooms in the same building, and each room has a set of four similar roommates, who all throw similar parties.

What is the building, what are the rooms, who are the roommates, and who are the guests?

I think the building is an

The rooms are

Combustion chambers (Cylinders)

The roommates are

The intake valve, the piston, the spark plug and the exhaust valve

The guests are

A mix of air and gasoline.

• Probably right, but the explanation is a bit off. If your solution is correct, the second roommate should have kicked out the guests after the second door had been opened by the fourth. Commented Sep 5, 2019 at 15:57
• Very good @hexomino! In my intended answer, the roommates are rot13(gur sbhe plpyrf bs n sbhe-fgebxr ratvar: vagnxr pbzcerffvba pbzohfgvba rkunhfg) Commented Sep 6, 2019 at 7:49