What makes Anomaly interesting is that it's obviously an evolution of the tower-defense genre, even though it's clearly a new genre as well.
Video games are complicated. They didn’t start that way, the rules of Pong should be obvious just by watching, but that simplicity can’t last. People demand more. Compare Doom to Battlefield 3: in one you can’t even look up, the other has more commands than there are buttons on a controller. This demand for increasing complexity is something that affects all entertainment (just compare Die Hard to Live Free or Die Hard), but it’s particularly troubling for games because keeping up with that demand can limit the audience. This is something other people have written about, and I’ve got no interest in repeating their points here. Instead, I’m interested in where a gaming genre goes once it’s reached that tipping point of complexity.
Anomaly: Warzone Earth is a reverse-tower-defense game in that you play as the “creep” rather than as the “tower.” You control a little man who has to guide a convoy of military vehicles through a maze of streets populated with alien turrets. Along the way, you can place things like smoke bombs or decoy units that protect your convoy. It’s the first of its kind or at least the first to meet with any kind of critical and commercial success. What makes Anomaly really interesting is that it’s clearly an evolution of the tower-defense genre, even as it’s clearly a new genre as well.
It’s a combination of genre iteration and regression.
The basic idea is iterative. It advances the genre in such a way that introduces new gameplay possibilities. Everything else is regressive.
How the avatar is utilized: in early tower-defense games, your avatar was just a tool for placing turrets, but more recent tower-defense games have made the avatar an important part of your defense. In Toy Soldiers, you take direct control over turrets. In Orcs Must Die!, you can upgrade your own weapons and magic. The same applies to Trenched/Iron Brigade, and Monday Night Combat even has an entire multiplayer built around the avatars. In Anomaly, your little soldier is just a tool for placing “turrets,” i.e. the defensive actions that protect your convey.
The number of commands at your disposal: if your defensive commands are the equivalent of turrets, then Anomaly is an incredibly sparse game with only four commands. Most tower-defense games have dozens of turrets in addition to whatever abilities that your avatar has; throw in multiple towers to protect and various environmental hazards, and you’ve got a genre that’s evolved by adding system on top of system on top of system. Anomaly strips away all that to give us a simpler game.
This mechanical regression makes sense given the genre iteration -- Anomaly really does represent a new genre. For as much as it relates to a tower-defense game, it is not a tower-defense game.
Playing Anomaly is like watching a divergent species evolve. The same process of iteration that made tower-defense more and more complex also gave rise to something new, and because the new genre is forging new gameplay possibilities, it currently exists as something far more simplistic than its brethren. Reverse-tower-defense games are not going to replace tower-defense games, both can exist side-by-side. They are simply two genres with a common ancestry.
And I believe that this is the natural progression of any gaming genre. Tower-defense’s humble beginnings seem quaint now, so does a game like Doom. As first-person shooters grew more and more complex, we got games like Mirror’s Edge and Portal. While the first-person platformer hasn’t really taken off as a genre, the first-person puzzler certainly has with Q.U.B.E. on the PC, and Quantum Conundrum coming to XBLA.
Genres need this kind of iteration to grow and stretch their own boundaries, but the tricky thing about iteration is that it builds upon pre-existing knowledge. If you don’t already have that knowledge, you’re left behind. However, I don’t think that this is necessarily a bad thing because eventually that iteration results in entirely new genres that are simpler and easier to get into, then the cycle begins again. Simple beginnings leading to ever more complex games until someone comes up with a new twist that leads to a new genre.
Maybe in a few years reverse-tower-defense will be everywhere and everyone will be sick of them, and just when the genre seems to have reached a saturation point. someone will have an epiphany that will lead to something new and exciting. I don’t know what it will be, but I look forward to finding out.