Space Station: Frontier

The folks at Origin8 have already proven their mastery of the strategy genre on the iPhone: they're the makers of popular tower-defense titles Sentinel and Sentinel 2. Space Station: Frontier takes place 100 years after the events of Sentinel 2: Earth Defense. Space Station: Frontier is no tower defense game, however; here, you're in charge of a mining operation in a dangerous area of the solar system, and you must simultaneously gather resources and defend your ship. Space Station: Frontier is a terrific strategy game that with enough twists to make it stand out from the crowd.

The meat of the game is in Campaign mode. Here, you'll struggle through the ten missions while waiting for your back-up to arrive. Ironically, it's the 100-year-old Sentinel that comes to your "rescue." Each mission requires you to either survive for a set amount of time or meet a mining quota; either way, you'll need to fend off enemy ships whilst mining enough resources to build up your defenses.

Your ship is floating in the middle of the screen, surrounded by scattered asteroids. You can build three main types of structures: miners, weapons, and support structures like power generators and repair drones. Initially, you're limited to a miner and a laser turret. You'll need to harvest energy in order to build each machine; while your ship generates a small amount on its own, miners must sap resources from nearby asteroids to provide with a sufficient supply. Enemy ships will fly on-screen at certain intervals (you'll get a heads-up beforehand). However, you can't just build willy-nilly; machines don't work on their own. A network of power nodes is required to supply energy to your structures. This adds an interesting aspect that's missing from many tower defense games, and forces you to place your structures strategically; one blasted node is all it takes for your complex network to lose power.

The two other modes—Survival and Mining—are basically free-play sections from campaign mode. In Survival, you're awarded based on how long you survive; in Mining mode, you're trying to mine as much crystal as possible. However, both these modes serve a definite purpose. Your ship exists outside of each level as a continuous structure...meaning that you can upgrade it from the main menu. The Shipyard screen presents an array of permanent upgrades, ranging from blueprints for better weapons to increasing the ship's health. At the end of every completed level you receive credits that can be used in the Shipyard. This is a key area of the game; it's simply impossible to complete all ten missions without upgrading your ships.

On the whole, the gameplay is a lot of fun, with a surprising amount of depth. New weapon types (laser interceptors, missile launchers, etc.) allow you to keep up with tougher enemies, who often hover just out of range of your standard weapons. The choice between more miners or more weapons is a constant strategic tug-of-war, and the sense of impending doom is almost a constant. This isn't an easy game, either; you can't barrel through the ten missions without re-playing some of it (or the Survival / Mining modes) to earn more credits.

The interface is similar to what we've seen in the Sentinel games: pinch-to-zoom allows you to view the map at almost any scale you want, and the graphics hold up nicely regardless. (They do seem a little blurry if you zoom all the way, however.) All building must happen in real-time, and the intuitive controls are therefore much appreciated. Lag is minimal, but when hundreds of enemies swarm on screen in later levels...well, it is apparent. OpenFeint integration automatically uploads your scores, and achievements are also integrated.

While Sentinel is a great strategy game, it isn't perfect. For one thing, I wish there was a lot more content. It doesn't take too long to get through the 10 campaign levels, even with the need to go back and play other modes to earn credits, and once you finish those the game loses some of its fun. Graphics and audio are both good, but not blockbusters. When you finish a level, the game dumps you back to the main menu without preamble. It's a bit jarring, especially if you wanted to continue the Campaign mode. And then there's the originality factor; while Space Station: Frontier has some great features, many of them aren't unique to this particular title.

Still, despite the low number of included levels, Space Station: Frontier is a blast. Strategy fans should enjoy its mix of real-time strategy (RTS) and tower defense (TD) elements, and the upgrades available in the Shipyard do give you an incentive to replay levels. The need to manage resource harvesting, weapon-building, and power networks concurrently makes it much more participatory than a boring old tower defense title. And, really, what's not to like about blowing up alien ships? Space Station: Frontier is a well-produced strategy title, and I thoroughly enjoyed playing it...while it lasted, anyway.