Space Invaders is an oft-copied formula that few developers seem to get right. Although alien movement and other mechanics are usually true to the original, it's the timing behind the shooting mechanic that separates the pretenders from those who actually "get it."

On a base level, Decimation X3 does a more than admirable job of cloning Space Invaders. But, after one round, you'll find it's something entirely different. Though it still holds to Space Invaders's basic gameplay tenets, Decimation X3 gives the old formula a massive kick in the pants.

Decimation X3 's presentation suits its play style. Everything is simple and blocky, but with a great "neon pixel" style. It's hard to describe, and really screenshots don't do the game any justice - it's simply something you need to see in motion to really appreciate. You begin with a few simple shapes, but as your ship powers up and the game kicks into full swing, the screen bursts into a cacophony of flashing pixels.

Music is another strong suit. In the past, I've said the best game soundtracks are the ones you don't notice. They just blend into the background. I've recently revised that stance, and Decimation X3 stands as a great example of my new-found appreciation of game music. Rather than simply blending into the background, the music enhances the gameplay, adding just that last boost of adrenaline.

True to its roots, gameplay is straightforward; lines of enemies drop from the top of the screen while you, playing as a lone ship, shoot at the incoming waves of enemies and attempt to keep them from touching the ground.

Where Decimation X3 differs from Space Invaders is in the number of power-ups at your disposal. As you kill enemies, they'll drop power-ups that enhance your odds of survival. Some offer a simple point boost, though others increase your rate of fire, ship's speed or even give you a set of shields to dodge behind when enemies fire back. It's a simple formula, and works incredibly well.

Another difference is the inclusion of bosses. Every couple of waves, you'll need to face down giant bosses. Most take up a giant portion of the screen's real estate, but still move in the same pattern as normal enemies. Since they require multiple hits to kill, you'll have to figure out the best strategy to quickly destroy them before they hit the bottom.

The best thing Decimation X3 has going for it is the pacing. The game starts out slow enough, giving you enough time to figure out the mechanics and get a feel for the game's timing (shoot where the enemy will be, not where it is now). Once you've got the basics down, it starts to throw numerous enemy configurations, each offering a slightly different challenge.

Decimation X3 is separated into two core modes, which relate more towards difficulty than anything else. One adds the option of shields and the other doesn't. The "No Shields Allowed" Challenge Mode is meant as the harder of the two modes, though I actually found it easier. Although shields offer protection from enemy shots, they also limit the amount of firing space. Unless you decide to just fire through your shields, dodging between shields and shooting requires a slightly altered play style. Without shields getting in the way, I felt like I had more strategic freedom.

One of the very few complaints I have against Decimation X3 is the lack of instructions. Even though its not an incredibly hard game to figure out, a screen detailing what each power-up does would have helped. I was able to figure out a few of them the second I picked them up, but others -- like "B" -- took me a bit longer.

The real magic behind Decimation X3 is in how it manages to take a handful of simple play mechanics and wrestle them into something chaotically complex. All you're doing is shooting at enemies, but every new mechanic offers a new decision. Timing is still at the heart of everything, but between collecting power-ups and dodging enemy fire, you're constantly forced to make numerous split-second choices. Go for the falling power-up and risk getting hit by a slightly faster falling enemy shot, or let it fall and make due with what you have.

Eventually, you'll swear the entire game is conspiring against you. Enemy waves hit faster than you can shoot them down, and giant bosses plow their way into the field. Even the visuals start to turn against you. The more enemies you destroy, the heavier the shower of pixels gets, eventually masking enemy shots. Of course, you've got an arsenal of friendly power-ups, which helps take some of the edge off. You still need to learn how to time shots, but when you're packing a fully-powered spread cannon, you can afford to fudge the timing just a bit.

Tossing in additional players adds another layer of complexity. The goal is survival, but everyone has their own score. Although you want to help your fellow players out, there's always the temptation of wanting to beat everyone else's score. There's no tangible advantage to having the higher score, but competition will do strange things.

If the promise of addictive, fast-paced gameplay isn't enough of an enticement, the price should do it. Decimation X3 is only a dollar, and I'm more than certain everyone has a few extra MS points laying around in their account. I can safely say I've lost just as many hours to Decimation X3 as I have to some retail releases.

If you enjoy shooters, or just feeling a bit nostalgic, Decimation X3 is a must buy.