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.