Editors' take: Space Station: Frontier HD ($4.99) takes elements from tower-defense-type games and traditional RTS games to make an enjoyable and challenging experience with tons of replayability. The object is to defend your space station from attack by building out a defense structure of laser turrets, rail guns, missile launchers, and other weaponry. But to build all of these items, you'll need materials which you'll mine from nearby asteroids, all as a part of your multinode structure you build around your station. To build your structure, touch and drag an item from the bottom of the screen to a place where you can connect it to your space station's network of nodes.
There are a few different game types including a campaign to play through, offering several levels with specific challenges. But you won't be able to complete the campaign without weapons and upgrades you buy at the Shipyard with money you earn by playing the other game types. Game types include Survival, Protect, and Miner. Survival mode is the first game type unlocked, where it's your mission to efficiently mine resources and defend your space station from wave after wave of attacking ships. This will be where you spend most of your time early on, trying to last as long as possible to make money so you can unlock more weapons and upgrades.
Even with all the weapons unlocked, you still won't beat Space Station: Frontier HD without developing a sound strategy of defense. To build your defensive structure, you'll need to build out nodes for your weapons and mining equipment to connect to. Your weapons and mining equipment run on power from the space station or power generators you connect to your nodes. If you don't efficiently use your power, you'll run out in larger battles, which renders your weapons useless. The nodes you build are vulnerable to attack too, so if an enemy ship takes out a connecting node (disconnecting it from the space station and connected generators), all the weapons connected to that node will power down.
Space Station: Frontier HD effectively uses both RTS and tower-defense gameplay to make for an incredibly addicting and challenging game. With three game types, tons of weapons and upgrades to unlock, and a Campaign mode that requires you to play through the other game types to succeed, Space Station: Frontier is a well-rounded and well-designed game that's perfect for any strategy gaming fan. One word of warning: once you get sucked in, this game is very hard to put down.