This is a fantastic game with good physics, good graphics, and good gameplay that anyone with a PC should get.
Graphics - The graphics are awesome. Sometimes you forget that you are playing a game. You actually get attached to the characters of the game, and you feel like you really know them. In one level "We Don't Go to Ravenholm" there is a pair of legs hanging from the tree, and you when you see them you feel like something bad happened here, and you are freaking out and peaking around every corner before you go around it. Everything has extensive detail, especially the blood it looks very life-like.
Sound - There isn't much to say about the sound, except that it is very good. When you fire a weapon you can hear it echo according to the environment you are in. When someone is talking to you and you turn around it sounds like it is actually coming behind you. You feel like people are actually talking to you and not the character in the game.
Interactivity – In this game there is pretty much nothing you can’t interact with. Every time you shoot something there is going to be a bullet hole in it. You can pick pretty much everything up including garbage, cans, boards, and anything else you can think of. You can break pretty much anything that comes in your way. Whether it be a board, or even a person for that matter :P.
Overall - This is my all-time favorite game. If I were you I would get the Game of the Year Edition, which comes with Half-Life 2, Half-Life: Source, Counter-Strike: Source, and Half-Life 2 Deathmatch. You can find it at a local store for around $ 40 - $50. Overall I give it a 9.9/10. I would like to make this game more well known because not a ton of people have heard of it, I think that this game would be on everybody's favorite list, if people were more inclined to buy it then say it is just another game on the shelf.