It was so simple that I've been unsure as to how creator Bizarre Creations could deliver a worthy sequel. Multiplayer and new enemies seemed like obvious choices, but could Bizarre really iterate on the core gameplay all that much?

Well, yes.

Along with the expected new enemies and four-person offline multiplayer, Geometry Wars 2: Retro Evolved 2 packs five new modes in addition to the original's Survival. Why no online multiplayer? "There's too much going on to do this over Live," explained Microsoft director of digitally distributed games Scott Austin.

King fills the battlefield with frequently appearing and disappearing circles, which serve as a safe haven untouchable by foes. And, of course, there's a twist. You can only fire from within those bubbles.

The result is a frantic race from haven to haven as players swerve to avoid foes and use their temporary base location to depopulate the landscape. The rules are simple and clear, and the gameplay is just as intense as ever.

Waves builds off a player's tendency to stay around the walls, transforming boundaries from a good defensive location into a death trap. It starts out simple as an legion of spear-shaped foes shoot from the entire length of a wall, moving quickly across the battlefield.

You're constantly on the lookout for the next spawn, camping out in the center and shooting frantically as they appear. After a few waves, all hell breaks loose as the series' regular enemies start to show up as well.

The last mode I sampled built off the Pacifism achievement from the original Geometry Wars, which had players attempting to survive for 60 seconds without firing a single shot. Needless to say, that was much harder than it appeared to be.

You obviously can't shoot, but you can still destroy foes by flying through one of the many explosive gates that appear on the battlefield. Problem is, there's not much margin for error--you have to fly through a pretty small target to trigger the explosion--and the explosions themselves are pretty weak.

The trick is to play it smart and attempt to lead a giant swarm of enemies as close to the randomly-located gates as you can. Again, it sure sounds simple, but the execution is something else entirely, especially as the enemy population grows.

Offline four-person multiplayer works just as you'd expect it to. Each of the six modes are playable, bringing high tensions through both cooperative and competitive game modes.

Of course, the extra neon-flavored chaos that three other players brings to the mix also means it's pretty easy to lose track of your ship. The solution, it seems, is to pay close attention and make sure you know which color you are.

I was pretty hesitant going into Geometry Wars 2, but I'm relived to say that the new game modes certainly add some new challenges and a breath of fresh air while retaining the original's simplicity. I've gone from dreading the sequel to craving more, and its August 6 release as a dowloadable Xbox Live Arcade title can't come soon enough.