What's it all about.
Spawn AI controlled creatures against human players and other AI, and do it along other teammates so damage inflicted is proportional to coordination and timing. That's the idea more or less. Customizable NPCs give an extra twist to the whole thing, allowing different tactics and level interactions.
If I had to explain it using already known concepts, it would some sort of mix between Zombie Master and Left4Dead's versus. I'm not a ZM player myself, but the basic idea is pretty similar I guess. The concept is taken to another level though, there's no single godlike player but several-less powerful so they must cooperate to maximize their attacks. Add to that an important difference: both teams start the game as gunfighters, only when a player is killed goes to ‘ghost state' and can spawn stuff. Therefore, there's additional interaction between live and dead players from same team. Finally, there's no direct NPC control unlike a RTS, players may order their minions to attack directly (rush) or await until being discovered (ambush).
There are many factors which made me wanted to create something like this. Artificial intelligence is one of the coolest things from a game developer perspective, building an AI framework from the ground is an enormous task though. As a Source developer, the engine is quite powerful in this aspect so no large effort required. The new NPC classes are familiar to FoF players but they are new code wise, their basic behavior is quite different from DM/co-op AI.
AI is already pretty important in multiplayer FPS field. Players demand experiences beyond the traditional team versus landscape. Adding AI is a tricky matter though. Unresponsive or ‘dumb' AI may just take the fun out. It's still something to be seen, but I certainly took lot of care to avoid such issues.
I also wanted to offer an experience which wasn't solely based on FPS combat/aiming skills. Frags matter in Fistful of Frags, obviously. The competitive aspect used to be the driving factor for many mods, now isn't enough to create a community around a mod like this. Getting past a level of competitiveness hurts unless there are tournaments, leagues, etc. Players in public servers just want fun and everybody has no bot-like accuracy. So this new mode offers two different but complementary experiences: FPS and NPC management done in an original way.
This is like a mod inside another mod. Originally meant to be an autonomous project, there was some ties with FoF and it could be a worth addition. So I went for it along some other important additions you'll see in 3.5. My intention is to preserve FoF as the team versus mod it always was meant to be, so a new project should spawn from here if all goes well. There's a clear path I want to follow and this is just the beginning. During the upcoming days I'll try to showcase how cool are the new NPCs, there's more :)