Half-Life is one on the few FPS (First-Person Shooter) games that has a good storyline, and that's just ONE of the things that makes it a great game. The story is pretty vague (nobody's written definitive anything about it yet, but I'm working on that), but it goes something like this: It was just another day on the job in a top-secret research facility in the New Mexican desert... Until you (Dr. Gordon Freeman) put the sample into the sensor. Then all hell broke loose; aliens "comin' outta th' damn WALLS!" (to quote someone from the addon Opposing Force), a USMC death squad sent in to "contain the situation" (read: Kill everyone and every thing on the base except yourselves), and stuck in the middle of it, you; a 27-year old child prodigy with a cool-looking environmental suit and a gun (which you have to find). To make matters worse, just about everything is trying to kill you.
The AI is excellent; the human soldiers will provide covering fire for each other, will use grenades to flush you out (very effectively, too), and will even refuse to follow you if you deliberately injure them (friendly NPCs exist in the game, which is rare). Realism takes a bit of a back seat to fun, though, but is is somewhat realistic. You have to reload occasionally, your shots will leave marks on the walls and will sometimes ricochet (harmlessly), and you even fire tracers every so often!
The AI is excellent; the human soldiers will provide covering fire for each other, will use grenades to flush you out (very effectively, too), and will even refuse to follow you if you deliberately injure them (friendly NPCs exist in the game, which is rare). Realism takes a bit of a back seat to fun, though, but is is somewhat realistic. You have to reload occasionally, your shots will leave marks on the walls and will sometimes ricochet (harmlessly), and you even fire tracers every so often!