Before You continue with this please make a backup copy as You'll be changing a file for this. Now, find the default.cfg file. Go to GameData/indy/default.cfg and edit it using notepad. (Be sure to back it up first)
Change the file to read as follows:
Save the file and run the game.
You will now have access to the builtin cheat mode with the following cheats:
Collect all artifacts in the game to unlock an art gallery.