Making a new map, stuck on one of the gags.

Whoa whoa. This is your first map? I think that really ambiguous, even the "pro's" have hard time with that.

This isn't meant to disgourace you.

I don't think that's a gag. The word you are looking for is a gimmick.

If you just want to open and close doors, you'll want to use func_door. You can change where the players spawn by enabling and disabling the spawnpoint/respawnroom/visualizer entities.

As for the logic setup, you'll probably want to use a math_counter in tandem with a logic_case. Have the goal trigger send the math_counter an Add 1 input on score:



Then, have the math_counter send its value to the logic_case:



Set up your case parameters like this:



And last, set up all of your inputs for opening and closing doors, and changing spawnrooms:



You can continue to add more case statements if you want things to happen on 4, 5, 6 points scored etc.

low gravity pass time sounds intense, Also i's suggest looking at a decompiled rd_asteroid to see how valve does it. You might find the material's normal map does a lot of the work for you