Revolutionary indeed...
Sound:
Very good voice acting , music and sound effects .
Gameplay:
Fast paced gameplay , with the ability to strafe , run , 2 jump types with your character .
Many weapons along the way and enemies .
The game length is good , you should have a long way till you complete the game , which is great .And you won't get bored , there is always action and some puzzles .
Great gameplay !
Graphics :
The graphics are great for it's time , and the game runs on a old PC very good .
Very detailed , no random areas with nothing in them .
Story :
The story is original and i won't spoil it ,it's a very good story .
And you get immersed into it .
It inspired many great mods too , and a awesome sequel .
If you like FPS games , you will like Half-Life .
I rated it 9.5 and not 10 because some improvement can be done .