Combining elements of real-time strategy games, shoot 'em ups and line-drawing games, Into the Blue SD has the potential to be a phenomenal iPhone game. Unfortunately, while what Into the Blue SD offers is enjoyable, there's just not enough of it to keep gamers coming back

Gameplay in Into the Blue SD is intuitive, with users using the touchscreen to control and fire a blue mounted cannon in the center of the screen. Enemy ships, colored pink, regularly appear and it is your job to shoot them down before they take out your cannon.

What makes the game stand out from the rest of the shoot 'em up games cluttering the App Store is that it brings resource gathering and management into the mix. As you progress through the game's levels, you must not only defend your cannon, but also the transport ships capable of harvesting minerals. These can then be spent on a number of different upgrades: Anything from additional transport ships to automated torpedo towers.

As you play through Into the Blue SD, each level brings with it a unique condition for success, such as keeping three transport ships running, mounting four torpedo towers, or even protecting the ship of a visiting ambassador. This, in addition to an increasing amount of items available for purchase, helps spice up what can be rather repetitive gameplay.

The problem, however, is that Into the Blue SD only has nine levels. While they each do run on the long side for an iPhone game, they can all be completed in two hours or less. There is an option to ramp up the difficulty, but instead of dramatically increasing the game's speed or the viciousness of your enemies, this option mostly just makes items in the shop more expensive.

The length of the levels causes some problems as well. Not every game on a mobile device has to be a quick in-and-out experience - there's certainly room on the iPhone for long, in-depth gaming experiences. However, the gameplay of Into the Blue SD, while entertaining, is rather shallow, which means that some of the longer levels can grate on the nerves of even the most patient players, and aren't really suited for when you only have a minute or two to kill.

Into the Blue SD does add some additional gameplay opportunities beyond its nine levels, however, with a Survival mode as well as a Hyper mode. Survival is pretty standard fare, encouraging gamers to go as long as they can without losing their central cannon. You are allowed to use whatever items you have unlocked through normal gameplay, but, as mentioned above, Into the Blue SD isn't the deepest game, and there's only so much time a gamer would want to spend playing it.

The game's Hyper play mode, however, is much more interesting. Not only does it speed up the gameplay, but it also allows you to use the iPhone's multitouch capabilities to keep up with the action. This means that you can simultaneously shoot your central cannon in two directions, shoot while directing a transport, or move multiple transports at the same time. This is a welcome addition to gameplay, but it raises the obvious question of why it was not included in the normal levels as well.

Despite the limited gameplay options and replay value, Into the Blue SD has a lot going for it. Unlike many games in the App Store, the controls are not only intuitive and accurate, but they're well designed with the iPhone in mind. The cannon tends to shoot just above where your finger touches (as indicated by a helpful crosshair), which helps gamers see where they're firing at all times.

With a normal purchase price of $1.99, however, Into the Blue SD just doesn't offer enough gameplay to make it a must-buy item. While hardcore fans of both shoot 'em ups and resource management might enjoy the time they spend with the game, it will ultimately be far too short to justify the purchase.

Final Score: C-