5 Type your CD Key into Steam!Shifter47 | 29/01/2009 | See all Shifter47's reviews (1)This game is a masterpeice that was the forefront of the genre when it was released and is still considered one of the best FPS's ever to this day.It has a perfect blend of action and puzzles with a superb storyline that will keep you gripped throughout. The added bonus of buying the Sierra retail copy is that registering the CD Key into Steam gives you the full GoldSource collection!! You get Half Life, Counter Strike, Day of Defeat, Richochet, Blue Shift etc. All the Valve GoldSource games for a tenner!!If you consider yourself a PC gamer there is no excuse to not own this game.