To the midway point in the first Halo game, it seems like a fairly standard shooter. Sure, the bullets are often blue, and the guns carry names like the "Needler", but you're still engaging in straightforward firefights with enemies who have tactics-driven AI (even if those tactics are a little... odd in places).
**we're looking at you, grunts**
In the seventh mission, things take a distinct turn for the survival horror. First, you meet a terrified marine who mumbles incoherantly about body-snatching monsters. You then go into a ruined room with a dead marine, who conveniently recorded a bit of video in his dying moments...
Suddenly, the room begins to fill with a brand new enemy. The "Flood" are essentially parasitic zombie stand-ins, and suddenly the game is completely different. You'll be running away from fights almost as often as you'll be starting them. You'll be placed in locked rooms and told to hunker down with hundreds of enemies until the room is unlocked. You will kill lots of
But the first time you take on that first room. The music change (from sad, string filled orchestration to a very grim-sounding churn), the tension. It's all very nicely cinematic.
...and now it's here for you to take in again.