Five very simple levels. Mostly, they emphasize a specific play style, or a specific weapon. Carnage rates are high.

Three levels. Pfhort McHenry comes with an authentic flag. Intrepid Death relies on fake walls for secrets.

A small diamond-and cross configuration, with a pit in the center. Stay out of the pit. Textures will make your eyes hurt after a while.

A small, tall room with stairs around the outside, a couple of protected rooms with big weapons (and teleporters as the only entrance), and sniper pillars. Vertical distance is big enough that you actually have to aim.