Check out this under-appreciated gem of a show!
The dark, twisted brainchild of Edmund McMillen and Caulder Bradford.
A security guard is trapped in a bunker, with a strange creature crawling around.
When you beat Portal you're treated to this song. It's called "Still Alive" by Jonathan Coulton (http://www.jonathancoult on.com/). Loved it so much I made it into a video. Enjoy!
Edit: Added in music credits. Thanks!