Geometry Wars: Retro Evolved 2 improves upon the original in every imaginable way, and then some.
The first change you'll notice is that you're no longer restricted to one game type. This game comes with six, each one different than the last, and each one requiring a different strategy to be successful in.
You start off with only Deadline available. Deadline is basically your standars Geometry Wars, but with a 3:00 time limit in which you try and accumulate as many points as possible. After playing through this game type a few times, you'll unlock the next one, which is called King.
In King, there are blue circular zones from which you can fire from, and enemies cannot enter. However, you cannot fire from outside these zones. And as soon as you enter one, it slowly deteriorates. So in order to survive, you'll have to plot your paths from zone to zone beforehand, and be sure to clear a path to your next safety zone before you leave the one you currently reside in. The longer the game goes on, the more enemies appear, and the more difficult it becomes to make it from one zone to the other.
After playing through that a few times, you'll unlock Evolved, which is your standard, no time limit Geometry Wars. Now here I'll detail some changes that make even this game type different than the original. Your ship no longer gets "upgrades", and there's only one gun, all the time. However, that one gun is decent enough for you to make it through the most crowded areas unscathed if you're skilled enough. Also, the multiplier. The first game capped at x10; this time, there is no cap. You no longer get multipliers just by killing enemies, but you must collect small green diamonds called Geoms in order to raise your multiplier. It's perfectly normal to have multipliers in the multiple 100's now.
As such, your scores from the first game will seem tiny now. While 1,000,000 was an accomplishment in the first game, you'll find yourself putting up 10 times that with even less effort. This is in most part due to the fact that your multiplier doesn't reset when you die, allowing your score to pile up until you lose all your lives.
Next up is the Pacifism game type, which takes the achievement from the first and turns it into it's own game. In it, the only enemies that show up are those normally harmless blue diamonds, but in this game they pile up, and fast. You can't fire, so you must rely on a new weapon/enemy; gates. I say weapon/enemy for a few reasons. It is a weapon in the sense that when you fly through them, they will explode, killing any enemies in the area (this is how you clear enemies in Pacifism). However, if you hit the orange edges of the gates, you will be killed instead. It takes precision, just as a Pacifism game should.
Up next is Waves, which you may recognize from PGR 4. In this game type, lines of fast orange enemies will fly from one side of the map to the other, and you must avoid getting hit by them. You can shoot through them and allow the rest to past by you, but the enemies quickly add up, and it can get hectic with walls of enemies flying from every direction.
Finally, there's Sequence. Here you will play through 20 increasingly difficult stages, and there are 3 ways each stage can end: You kill all the enemies before time runs out, you survive until time runs out, or you die. Once any of these 3 happen, you move onto the next stage. Lose all your lives, and it's over. It sounds easy, but the stages get incredibly difficult, and it will take all your skill to make it through all 20.
The game offers up your standard 12 achievements, and they're actually quite fun, ranging from dodging 8 lines of enemies in Waves, to rubbing your ship completely along all 4 walls during pacifism. Some are easy, and some are very difficult, and it's overall alot of fun to try and get them all.
Graphics and sound are both fantastic. The explosions from enemies cause fireworks to burst in the background, nukes send ripples through the background as enemies disintegrate into nothingness, and black holes flicker the colors of the rainbow as they stretch and distort the background around them.
So there you have it; Geometry Wars: Retro Evolved 2. Is it worth buying? Yes. So do yourself a favor, turn on your 360, and download what is by far the most addicting, fun, and arguable prettiest game available on the Xbox Live Arcade.