Released last week by indie developer allenp, Moon Rocks is an impressive little shooter-defense game that's pretty challenging and fun. Loosely inspired by the classic arcade game Missile Command, you're tasked with defending your little chunk of the planet's surface from an onslaught of asteroids, ice comets, enemy ships and plenty of other things that threaten to turn your base into Swiss cheese. Unlike the old 2-D style of Missile Command and many of its clones, Moon Rocks emulates a three-dimensional grid space for building your base. It doesn't really affect gameplay, since the falling asteroids are still two-dimensional (as far as I could tell), but it's a better way to optimize the UI real estate and manage your base. Plus, it just looks cooler.

If you don't expect too much in the way of back-story, you won't be disappointed—there really isn't one. In the campaign mode, you command a sort of mining colony or fleet, jumping from planet to planet to gather resources, while the enemy AI players try to do the same. The more resources you gather, the more towers and technology you'll be able to unlock. This is all managed through the map screen, which you'll see between each level (also giving you the choice of which planet to attack next, while your opponents do the same). Besides unlocking brand-new towers, you can spend points to unlock higher levels of certain towers, like your cannons and lasers. You can also spend points on technology to increase things like tower armor, tower cost and lots of other different upgrades. In order to buy most of your towers in-game though, you've got to purchase one or two Factories and place them next to the crystal-looking objects on your grid, which represent mines. Factories will steadily increase your resources, and you can upgrade them into Refineries to bring in the money even faster.

You get a fairly wide array of towers, most of which work in synergy with one another to provide the right firepower for the right situation, and the defense you'll need to fend off the asteroids and the special attacks your opponents will send your way. Your basic weapon is the Cannon, which can be upgraded three ways: speed, power and "frag," which makes the projectile explode on impact, bursting into more projectiles. The Laser can only be upgraded in power, but it's useful for focusing in on single targets like big asteroids. You've also got an Anti-Aircraft gun, a Solar Shield to protect your base, an Anti-Gravity tower to slow incoming asteroids, and a few other useful towers like the Air Base, which is used to send fighters over and attack one of your opponents. A similar tower, the Gravity Well, is also used to attack an opponent's base by hurling special asteroids at it, like the Ice attack to slow its towers, or a Radioactive attack to break apart asteroids into even more pieces.

The premise might sound a little confusing at first, which is why it's a good idea to read all the tutorial sections and click on the "?" icon in each screen, which labels the function of each part of the UI. Essentially, your main objective is to defend your base and destroy as many incoming asteroids as you can. That's how you ultimately win each level; by destroying more asteroids than your opponents. But you can also attack an opponent's base in the hopes of destroying a few of their own towers, slowing them down while they have to rebuild. They can do the same to you (and they will), which is why it's important to invest in an Anti-Air gun or two, and a Solar Shield. All of your opponents' data is in the upper-right corner of the UI. You can see a real-time graph of how many asteroids everyone is destroying, as well as selecting an individual opponent to view their actual base, or direct attacks toward them if they are gaining the advantage.

Analysis: There's no denying Moon Rocks has a steeper-than-usual learning curve. Without reading the Help section and playing the tutorials, you'll be flying blind when it comes to the more intricate aspects of the game—specifically, the mechanics between you and your opponents. But once you get the hang of it, the game doesn't feel detached or punishing at all (although it's still quite a challenge beyond the Easy setting). It's an interesting combination of arcade and casual Flash game elements, like a cross between Missile Command and a tower defense game.

There's a nice Quick Play option that throws out the enemy opponents and unlocks all your towers, allowing you to play as long as you can survive without any distractions. Unfortunately, there's no way to save your progress, even in Campaign mode. Apparently it's something the developer had to sacrifice to release the game on time. On the other hand, you can complete each map in an hour or two. Still, that's something not many casual players will appreciate. But overall, the gameplay is solid, the graphics and sound are stylized and respectable, and it's a pretty fun and unique game if you enjoy strategy-shooters.

Play Moon Rocks