How to play Half-Life 2 in 2D
Some clever clogs at Reddit has discovered how to get Steam to install Codename: Gordon, the 2D flash game originally bundled with Half-life 2.
According to Arlips, the user who posted this, the game vanished when the developers of the free flash game went bankrupt. Certainly, their site has vanished - here's a cached version. While Valve apparently took down the store page for the game and stopped advertising it in the Steam store, you can still instruct Steam to install it by copying this text into your browser's address bar:
You'll need to have Steam installed, running, and perhaps registered to handle the steam:// protocol, but it works. There's headcrabs, zombies, Combine soldiers, and even some dialogue options for Gordon. While I torch it from my hard drive for blasphemy, you should have a go. It's only 40 megabytes.