Finally, something new in the genre! May require some getting used to, though.
It's difficult to explain the game mechanics and even more difficult to play the game itself. You have a base, some energy and a Perimeter. The latter is a defensive energy barrier you can raise if you feel the need to. However, it consumes LOTS of energy, so it can't be kept up all the time. You can get more energy by building power plants and expanding your territory and Perimeter by terraforming, and you need energy for... well, everything.
The units you build are quite useless at the beginning, but you can combine different types of them to get them "upgraded" to better units. The trick is that you can morph them in the field, transforming your snipers into aircrafts to fly over terrain. You have a maximum of five squads of units, and while this may restrict things a bit, it sure does make everything a bit easier to understand.
I'm doing a poor job in explaining how the game works and I'm not even telling everything, so imagine how complicated the game really is. That's the best and the worst thing about it. It requires a lot of thinking. And a lot of clicking. And good reflexes. Even though it's complicated, it's also fast and the AI, while not being the brightest one out there (though it's not dumb, either), always has an advantage in numbers. So Perimeter can get very hard even for an experienced RTS player. But then, if it's challenge you seek, it's challenge you'll get.
Perimeter is a pretty game. If you zoom in, you can see cars flying around in your city bubble. Terrain is altered by gunfire and creature spawns, and it really plays an important role, because you don't get energy from spoiled areas. Besides, you can destroy buildings by destroying the surface they are built on. The music is good, and it catches the game's atmosphere well. There are only a few tracks, but all of them are quite long, so it doesn't get repetitive.
If you want a hard, beautiful and revolutionary RTS, Perimeter is a game you definitely shouldn't miss. However I don't recommend it to gamers who want everything simple and conventional. Simply because this game is neither.
P.S. I think the community is dead. Not sure, but I think it is. The game is, however, quite long, hard and extremely cheap. Besides, the expansion will soon be translated.