What are you playing?

[Lemonray]

Also considering that I'm only 5 hours into the game (including pause breaks and getting food) and am already halfway through, it's pretty short.

It is, but games that follow a linear path almost always are. Looking at a complete map of HL1's world will show you how small the place actually is, though I think Valve did a pretty good job of making it look larger from inside the game.

Seriously, though, one thing that really irks me is when I'm able to beat a game in several hours on my first playthrough. A few years back, I played through a certain game in seven hours, but after subtracting the two hours spent watching cutscenes I realised I spent only five hours actually playing. And five hours, for a game with one single player campaign and no multiplayer options is just not acceptable.