This is about an Apple II version of Portal, the cake acquisition simulator released in 2007 (not the similarly named contemporary Apple II game released in 1986). Note: this project is just for fun and is in no way endorsed by Valve, etc. While attempting to travel to the future to get a copy of Portal 3. I accidentally traveled to alternate-1987 and obtained a copy of Portal 1 for the Apple II!
In actuality I originally just planned to do the end credits. But the Apple II high-res mode has the perfect Aperture Science orange and blue colors, and one thing led to another...
Portal-appleII is written mostly in Applesoft BASIC. The full source code can be found as part of my apple II dos33fs utilities:
git clone https://github.com/deater/dos33fsprogs and look in the "glados3.3" directory.