How do I install an artpack on OS X?
First make sure you have StuffIt Expander installed, then download the .zip file, and double click it. This will create a new folder with the name of the artpack. Now Click on the GLtron.app icon, while holding down the ctrl key, and choose ‘Show package Contents’ from the pop-up menu that appears. Then go to the Contents -> Resources -> art folder, and drag the artpack folder their. Start GLtron and choose the new Artpack in the video menu, by pressing ‘enter’ or left/right on the Artpack entry.