Ok, I've been trying this. I have two separate maps, both of which have the same bit of corridor for the seamlessness. In map (I will call it here) aaa2, I have a door called aaa3en, trigger_changelevel, and a trigger_transition. I also have a multimanager. Now, what happens when first going through it, a switch is pressed, aaa3en closes, about 2.9 seconds later the trigger_transition and the trigger_changelevel (named the same, "changelevel") are activated, loading map aaa3.
In map aaa3, the conditions are identical. Except I have a problem. I can't get the door to open. So, I stick a trigger_once in there just in front of door aaa2en, to open the door. But then, going back through, pressing the switch, triggering the changelevel, I can't get through door aaa3en again. I can't put a trigger_once in there, because the player will activate it when coming in, closing the door, meaning that the switch makes it open, and therefore the player can escape through the door and get stuck when the level change occurs and leaves them stranded in the void a short distance away from the passage in map aaa3. And vice versa the second time around.
What I need to know is this - short of a trigger_multiple, which would activate door aaa3en/aaa2en every time the player goes in the passage (which would lead to the same problem outlined above) what would be a way to make each door open?
Right now I have a one-way level change which works. I need to make it two-way.