
The demo has the first two maps of the introductory mission, No Mercy, which are available in straight single player with AI buddies or in co-op mode for you and three live players (the Versus mode, where you can also play as one of the zombie boss characters, is not included in the demo release). A video intro introduces us to the setting in a bare minimal way; the four human characters are fighting the rest of the world which has been infected with the zombie plague two weeks earlier. There's no back story here; no reason why the plague happened and no hint as to why these four characters are together. It's just jump in, move from point A to B and shoot anything other than your teammates. (you can download the video intro right here at Big Download).
There's still apparently some humans still alive besides the four in Left 4 Dead. In the first demo level a helicopter flies over and via a speaker the pilot tells the team to head to Mercy Hospital. From there it's all about shooting and blood and lots of it. There's no difference in terms of gameplay between the four characters you choose from; whether you play as big tattooed Francis, old military man Bill, hot chick Zoey or bald black man Louis you still have the same weapons and items.
The two levels in the demo can be quickly taken care of in just a few minutes on the demo's Normal setting which indicates that the entirety of Left 4 Dead's single player experience (four chapters with five levels each) will be a fairly short one. The first has you and the team going down from a rooftop down to a street and finally to a safe house location. The other has you entering a subway system that leads to a final power plant location.

You can choose one of two weapons at first; the shotgun and the sub-machine gun. You also get a pistol with unlimited ammo (although you do need to reload it) along with a health pack that you can use to revive teammates. You will be doing that a lot in the game and your teammates will be doing that to you as well. Pain pills increase your health temporarily and there are Molotov cocktail and pipe bombs that you can throw. You gain access to more weapons at ammo dumps as you move through the demo (including an auto-shotgun, an automatic rifle and a hunting rifle).
Valve has said that Left 4 Dead has an AI Director which allows them to make the game slightly different every time you play. We played through the demo several times and found that zombies usually reappear in different configurations; zombies that appear in one portion of a level are missing when we played it a second time and then reappear in a different configuration the third time. We haven't played the demo yet on the two higher difficulty levels so we assume it simply gets harder and harder to avoid the creatures at those levels.
The two levels in the demo can be quickly taken care of in just a few minutes on the demo's Normal setting which indicates that the entirety of Left 4 Dead's single player experience (four chapters with five levels each) will be a fairly short one. The first has you and the team going down from a rooftop down to a street and finally to a safe house location. The other has you entering a subway system that leads to a final power plant location.

You can choose one of two weapons at first; the shotgun and the sub-machine gun. You also get a pistol with unlimited ammo (although you do need to reload it) along with a health pack that you can use to revive teammates. You will be doing that a lot in the game and your teammates will be doing that to you as well. Pain pills increase your health temporarily and there are Molotov cocktail and pipe bombs that you can throw. You gain access to more weapons at ammo dumps as you move through the demo (including an auto-shotgun, an automatic rifle and a hunting rifle).
Valve has said that Left 4 Dead has an AI Director which allows them to make the game slightly different every time you play. We played through the demo several times and found that zombies usually reappear in different configurations; zombies that appear in one portion of a level are missing when we played it a second time and then reappear in a different configuration the third time. We haven't played the demo yet on the two higher difficulty levels so we assume it simply gets harder and harder to avoid the creatures at those levels.

