@marislawrence linedefs (segments between vertices roughly defining either floor areas or walls) can be set arguments to do more than be a wall or a line on a wall, like be a switch or (in this case) be a portal.
Here are 5 rooms, the blue lines are the linedefs with the portal properties and I link them in such a manner they form a loop. The engine does the rotation/translation automagically
@marislawrence Yes and no actually. No because I started wanting to test *Doom modding something like two weeks ago I think and yes because I did try modding SRB2K (a total conversion of a similar engine to GZDoom) which is close enough in its level structure I could switch to similar tools and have minimal adaptation to pass through
@Ronflaix Incredible! Have you been playing with GZDoom for a long time?