I hate to say it but it was fun...
I ussually hate quiz games but it was about half-life so obviously I had to play it. You should add more questions or make a half-life 2: episodes quiz that you can update when episode 3 comes out. Maybe you could make a half-life 1 quiz. That has potential to be REALLY hard if you think about it.
Also I didn't like the whole chapter PW thing. Its good if you restarted the game and you put it in but don't make it required to move on. Also smexyalyx? ...Hmm someone has a hole in their pocket :P