what was that halflife2 mod that deals with the physics?

So what do I have to do? Download steam? And garrysmod will be playable in it?

You have to download install Half Life 2, install steam, then install garry's mod. And it will then be playable through steam.

You have to install steam before you can install Half Life 2.

and then....you pwn....

Here is my dirty garry's mod.

http://doublesmusic.com/other/Jimmy/alyx.jpg

ahaha nice pic