About extracting the code on Steam:
For starters, you will need to locate the games installation folder. By default the path should look somewhat like this:
Program Files\Steam\SteamApps\common\insertgamename
Older games like Tin Star will have simpler folder contents than newer ones. To extract the code of these older games, we will basically extracting the gamename.exe file to view its contents. You will need to have 7-zip installed. I do not know if this works with other extraction tools as well, it doesn’t work with WinRAR for me.
Right-click the gamename.exe, go to 7-zip, then “Extract to gamename\”.
This will create a new folder with all the contents of the .exe file. In there is a folder “scenes” which holds all the .txt files with the game’s code. I’d recommend opening them in Notepad++ if you’ve got that installed.
About newer games:
idonotlikeusernames has linked two methods to extract a game’s code earlier in this thread and you can find more detailed explanation to the nodejs method in a reply to that post:
This method will ultimately also result in a new folder being created where all the files have been extracted to and you’ll find the game’s code again in the folder “scenes”.