simple spiral stairs airlock

as the title says, simple airlock for a square foundaton using the new spiral staircase. includes a double airlock and a simple version. keep in mind that all the stairs have gaps between the steps EXCEPT the sheet metal one. the wood + stone versions also have a really open railing, making it easy to look down/up and shoot through. the sheet railng is a bit more covered, the armored one fully with no gaps. u can however stick signs to the railing, covering it up partly.