A central arena (more action on the ledges than the floor, at least for us), and some outside narrow passageways. Author says powerups and rechargers were kept to a minimum... I guess we have different definitions of "minimum". (There are 2 2x rechargers, and a 3x powerup, that I found...) Teleporters in the outside corridors make sure it's never hard to find spanker-fodder...

There's a central room, but most of the action is gonna happen in the outside rooms and hallways. Watch the nasty corner rooms...

Three enclosed rings. All the good stuff is on the top one, but you start at the bottom...