There is one instance of the game I actually solved a puzzle in an alternate way then Valve intended it, on my first playtrough.
Some of you might remember this specific room, right after the rocket launcher:
http://www.xs4all.nl/~dianajo/escape_010000.jpg
Yes, the vent was too high. And there was no obvious way to get in it at first glance...
So I eventually solved it like I would in real life:
http://www.xs4all.nl/~dianajo/escape_010001.jpg
But now that I've listened to the commentary in the game a few days ago, I found out that it wasn't meant to be solved like that. But rather like this:
http://www.xs4all.nl/~dianajo/escape_010002.jpg
http://www.xs4all.nl/~dianajo/escape_010003.jpg
http://www.xs4all.nl/~dianajo/escape_010004.jpg
Now I've been reading around some articles on the web. And it seems that my original solution is actually more popular than the intended one. I was wondering if this is the case on this forum aswell.
