What more can I say? A game in which you are fully immersed from start to finish. The game never stops!
You play as Gordon Freeman, a low ranking scientist whose only job is to follow orders and help carry out experiments. What you thought was going to be any old boring day turned out to be the greatest disaster in history! Whilst carrying out the experiment, there is a major error (or a resonance cascade in the game). This opens the portal to the alien universe, "XEN". Your job is to end this mess!
The game features impressive ai. I was convinced that I could make an unsuspecting alien grunt walk into the tripmine that I placed... but it refused to go anywhere near it, and backed away! I was then forced to shoot it to proceed. A waste of ammo and a mine! The game has many cool weapons, such as the shotgun and the mp5 smg. However, you also use some more unusual alien weapons too, such as the hornet gun and small vicious bugs called snarks.
One of half-life's impressive features is it's ability to play custom mods. This means you can instantly search for multiplayer and single player missions that both valve and other dedicated gamers have made. This means you will never get bored!
Bottom line: Thanks valve, you've made a masterpiece!