Dec 12th '17, 16:39
Platforms can trigger adjacent platforms. So, clunky solution would be:
Create Platform 1 and Platform 2. Platform 1 is the door the players will walk through. Platform 2 is a platform adjacent to it, hidden from the players' view, and extended the full height of a map (-9WU to 9WU). Adjust 2's speed so that the time it takes for it to move its entire length ends up being 15 minutes; make 2 activate adjacent platform "on deactivate" or whatever the setting is, this will activate Platform 1 once Platform 2 finishes moving.
You can adjust the height of Platform 2 if you want to make the calculations easier. Like, you could set its total height from -5WU to 5WU which is an increment of ten. You can also create series of Platforms 3, 4, 5, etc. to extend your time further, each one activating the one next to it when it stops moving. Also, making the platform "deactivate at original level" will make it travel twice as long as "deactivate at each level".
I'm doing this quickly in my head so my math might be wrong, but a platform extending from -9 to 9WU traveling at 0.1 WU/s should take 3 minutes to finish moving. So, if you have 6 platforms, with 2-6 being hidden platforms (that deactivate at each level) meant to just kill time, and Platform 1 being the door that the player actually sees and which opens after 15 minutes, then that should work.
There's a lot you can do with platforms (including creating day/night cycles) if you just understand all the tricks.