This is one of the most perfect games I've ever played. The graphics are flawless, the physics are flawless, the plot, storyline and characters are flawless.
I had hours upon hours of fun with this game. I was engrossed in what was happening around me but more impressed with how I could manipulate the physics of my surroundings. The original half life game raised the bar to a new level, and its sequel has done the same, putting other FPS games such as Doom 3 (which was released around the same time) to shame.