How to complete it:
Grab the shotgun and pipebombs from either end of the first room - Alpha. Head down either corridor towards the (anticlockwise) revolving floor - note that the blue edges don't revolve, so use these to move clockwise. Watch out for the drones as you grab the weapons from outside each hub room: a chaingun, RPG, freezethrower, and shrinker.
Return to Alpha room and open the door to find a portable medikit plus devastator and chaingun ammo. Hit the round green switch in the middle to open the first hub room. Now return to the revolving walkway to take on the newly released aliens and assault commanders - use the shrinker against the latter. More shrinker ammo can be found in the opened hub room.
It doesn't really matter which order you do the rooms in, but we'll head for the outside Beta room next. Grab the pistol and shotgun ammo, then open the door to find RPG and chaingun ammo, plus a healing atom. Flick the switch to open the next hub room and head for the revolving walkway to confront the released assault commanders. Inside the hub room is lots of shotgun ammo and a portable medikit.
Time to go to the Gamma room and grab some more shotgun ammo (if you really need it!). Behind the door there you'll discover chaingun and devastator ammo, plus portable medikit. Once again, flick the switch to open the next hub room. Return to the revolving walkway to take on more assault commanders and aliens. Inside the hub room is a nice supply of freezethrower ammo.
In the Delta room is some shotgun ammo, and a medikit in one of the corridors. Opening the door reveals chaingun and RPG ammo, plus a healing atom. Flick the switch to open the final hub room, then head for the revolving walkway to blast assault commanders and aliens galore.
When you're ready, flick all four switches in the hub rooms to open up the central room: when you enter, a big boss appears. Retreat back outside and blast him with the RPG until dead - it takes about eight good shots. Re-enter the room to summon another boss: use the same tactics. Grab the holoduke and devastator ammo before hitting that destruct button.