Twelve levels. These tend to be huge, open areas, with smaller side areas. Texture choices are odd, in some cases (and overabundant in most). The levels seem to get better as you go higher in the map set (although I encountered a freezing bug in the last level). A couple are extremely high in alien count.

A pretty interesting level, with lots of secret (or semisecret) doors. Flow is great, once you've figured out where these doors are... and there's a little something for everyone. Open spaces, tight corridors, hideaways... there's always a way out of wherever you are. Watch the double jugs (non-trivial to trigger, so you may not see them).

The focus recently has been on solo levels, but this is a pack of 26 consistently very good net levels. These guys like narrow raised walkways and sharp corners, but overall, flow is great, texture choices are very tasteful, and weapons are plentiful. There are some very cool tricks (I liked the stairways on Pseudo Bridge a lot), and nice lighting on several maps. No matter what size your group is, you should find maps you can die in here...The only downside is that they're actually asking for money if you like the maps. Update fixes a couple of small bugs

Take House of Pain, open up the outside walls, add crossed trenches in the center, and brighten up everything considerably, and you'll get this well-built large arena, equipped for up to 8 players comfortably. Nice roof...

A sequel to Lunar Fort. Very well-done, and quite playable... it's three levels, but only the second one counts, in terms of gameplay. Worth the download, for sure...

A large level with a few open areas, a suicide room, and lots of passageways that look the same. The room with the fluctuating pool has some neat features, though...

Two huge rooms (lots and lots of smearing) filled to the brim with aliens, and bobs, and S'pht'Kr. No weapons... you're supposed to do your fighting with what you can pick up off the dead bobs... Frame rates below 5 fps on a Q800.

Two levels. One is a conversion of Bob World HQ (no credit to Mark Conahan, the original creator), using the alien textureset, and the other is a small insanely busy arena with a raised cross in the center.

An arena level with a large pool in the center. Half of the bottom rises and falls slowly, making a good high spot (or missile block). Teleporters speed up end-to-end travel, and light switches control who's visible and who isn't...