If I was apprehensive about anything in Halo 3, it was the Flood.

Halo 1 has reached a certain legendary status amongst fans, but even it has a sore spot for many: the Library, where you navigate endless repeating dark corridors with endless hordes of only four enemies to fight: Human Flood combat forms, Elite Flood combat forms, Carrier forms and Infection forms. The level goes on a floor or two longer than it really has to, and only has a few tricks up its sleeve to make it seem fresh.

If Halo is built on a foundation of "thirty seconds of fun" then the Library was built on six helpings of five seconds of fun: shotgun a Flood form in the face, run away, repeat.

Of course, other Flood missions fared much better; they had better unit mixes, more varied terrain and encounters, as well as vehicles. 343 Guilty Spark had atmosphere oozing out of every pore as the Flood gave you the first real scare of the game. Two Betrayals gave you the dark side of Assault on the Control Room as Flood, Covenant and Sentinels took aim at each other and you while you tried to stop Halo from firing.

The Maw mixed it up by varing your objectives a bit, and by allowing you the chance to watch some interesting fights play out. The Flood themselves, though, were interesting to look at, but not so much interact with. When they didn't see you, they gurgled. When they did see you, they charged straight at you, firing whatever they had. If you had superior firepower and room to maneuver, it was no problem. If you had only one of those, or neither, you'd be in a world of hurt, not because the Flood outsmarted you, but because they overwhelmed you with numbers and clogged up your travel lanes with dead bodies. Or even dead Grifs.

Halo 2 added a significant twist to the Flood, but the game could only get so much mileage out of it. Instead of merely giggling with glee as you set off cascading explosions of popcorn Infection Flood, this time around the little devils scurried around more unpredictably, and raised dead Flood from the battlefield to face you once more if you didn't dismember them with a sword or blow them up with a grenade.

Once so raised, though, they were still the same old Flood. Four flavors, and one tactic.

How, then, would Halo 3 handle the Flood? More of the same?

I was relieved to find that not so. First of all, the Flood levels are broken up throughout the game. In Halo 1, once the Flood are revealed there's never a level where you don't have to fight them. 343 Guilty Spark shows you only token Covenant resistance before revealing the Flood. The Library dumps you into a Flood-only dark labyrinth. Two Betrayals lets you fight Covenant, too, but the Flood are always there. The Maw features Flood predominantly.

Halo 2 took Halo 1's journey-in, journey-out mission design philosphy and applied it to level pairs, some of which involve Flood. As the Arbiter, you fight your way into the mining installation against the Heretic forces, and fight your way out once the Flood are released.

In Gravemind, the Chief journeys his way into High Charity against Covenant forces, then fights his way back out again once the Flood attack.

The Arbiter's entire journey to the Index (Sacred Icon and Quarantine Zone) are predominantly Flood levels.

Halo 3 is far stingier with Flood levels, and then gives both Flood units and the environments you fight them in far more variety. The journey-in, journey-out design again applies, as The Storm brings you to the edge of the artifact the Covenant have uncovered, only to make you fight your way back out once a Flood-infected Covenant cruiser crash lands behind you, carrying a hidden message from Cortana.

Floodgate's areas are better lit and more wide open than other indoor Flood levels, though, and you immediately see far more variations of Flood. Not all of them simply rush straight at you, and some show some really interesting behavior, morphing into new forms in front of your eyes. You may see a form that is shooting you at a distance with something that looks like a built-in organic Carbine. Rush at it with a sword, and it'll immediately morph into a crablike form and scuttle away, or into a massive form resembling a Hunter to try and smash you to bits.

Not content just to let Infection forms raise fallen Flood, now they'll infect dead Elites, humans or Brutes that litter the battlefield in a gruesome transformation, pustules bubbling on the surface of the skin as you watch.

Then the game gives you a break from the Flood; they don't appear in The Ark, and you don't see them again until the end of The Covenant, and near the end of that level, they're your allies for a bit, before predictably turning on you.

Cortana is Halo 3's Library, the one gamers love to complain about. Yes, it's dark and quarters are cramped, but the level sacrifices nothing in terms of atmosphere without being so dark you can't see where you're going or what you're shooting at, as in High Charity. Like High Charity and the Library, the real treat here is seeing the plot advance through the back and forth between Cortana and Gravemind as you get closer and closer to rescuing your trusty construct companion.

While Cortana also breaks down internally into journey-in and journey-out, it gives you a break on the way back, as it's not necessary to go all the way back (plus, you get some help).

Halo also gives you the Flood to fight, but in a large, open area. You won't end up dying just because there's nowhere to run to in order to find more ammunition, or nowhere to retreat to while your shields recharge.

It was apparent after the first game that the Flood posed a special challenge: central to the plot, they cannot merely be discarded in favor of enemies that are more entertaining to fight, nor can they merely be made clones of those other enemies, the Covenant, without betraying their very nature, which is part of what makes them central to the plot. Halo 3 cuts through this Gordian knot by providing more variety, horrifying visuals, and oodles of atmosphere.

What was I worried about, again?