>>14863380
>Open steam.
>Install TF2, CS:S or any source game.
>If the game is not originally on your library install the game, and by that I mean start the installation and then pause it.
>get the ID of the game you need to play.
>Open steam_appid.txt and replace the game's ID with the one you copied.
>Launch from hl2.exe, you'll get an error.
>Congratulations, you "played" the game without fully installing it.