Crossfire!! is divided into 3 different sections.
Refer to the overhead map below for clarification.

The section with the green wall textures, I call the "Mushroom" because that's kinda what it looks like. The mushroom has a little river running thru it to cool off the reactor at the bottom. There are two little "secret tunnels" through the mushroom wall above and next to the river.

The other half of the level I call the "Metro" Area. The metro area is divided into two main parts, the basement and the "sig room" at the top of the big elevator. Off of the sig room there are two side tunnels that make for some very interesting chases.

The goals are off the central section of Crossfire!!, and are behind locked gates. To open the gates, you must start in a central cube (that means if you look straight up or down, you see the fuel center cube) and fly towards the door you wish to open. Triggers surrounding the center column will open the door for you.

This level has one Shaker and one Mega missle, placed under the waterfall. If you want to let them out, have someone wait at the top of the metro area by door "A". When the panel behind the missles is shot, door "A" will open, exposing another control panel. If you hit that panel before the door closes for good, it unlocks door "B". Inside door "B", you'll find the control panel that removes the wall in front of the big missles, and you're ready to rock.

Anyway, as long as no one is waiting by door "A" when you hit the panel behind the missles, you'll lock 'em in for good, because door "A" locks for good after only opening once. This means that it takes two people cooperating to let the shaker and mega missle out, so ask the person you play with if they want to use the big missles.