[squeaky-clean]

Portal 1 and 2 have amazing in-game developer commentary modes. Would highly recommend a replay with the commentary enabled to anyone interested in game design at all.

Can't watch with sound at the moment to confirm it's a good video, but this comes up in youtube

https://www.youtube.com/watch?v=x0uVg9nuaS0

[dzamie]

I wish more games had dev commentary like this. It's neat to peek into the minds of the developers, and can give good informal lessons on designing games and levels.

[c3z]

Check Johnatan Blow videos on You Tube

[leoc]

Team Fortress 2 as well.