honestly i wish it was that easy, but when I tried to make multiplayer, I either needed some server framework, which costs money, or an IP server system (much like minecraft) and then with the IP server system it was very laggy...
I don't know how to make multiplayer, because I can't model a player, or figure out how to make the multiplayer in the first place, (nor could I figure out room and entity syncing)
okay, in that case, you should check out Rooms and Doors on roblox, it's also a really cool game! but be prepared for absolute pain and hell (I recommend using deaf mode if its hard for you to hear A-60)
this is a cool game, but I would like to note, Rooms doesn't come from Doors, the subfloor is a reference to the game Rooms by nicorocks5555 on roblox, the inspiration for Doors