When Doom hit the market, everyone wanted to get their hands on it. Even videogame hardware makers wanted in on the action, which led to a variety of ports of questionable quality. One of the most infamous ports was for the Atari Jaguar — that one didn't even have any music! Slightly less infamous was Doom on 3DO — it was ported in 10 weeks and ran at a tiny resolution with an enormous border that occupied almost half the area of the screen! And now you can check out its source code!
The code was released by Rebecca Ann Heineman, the programmer hired in 1995 by the company Art Data Interactive to port Doom to 3DO in time for the holiday season. She was told that, before she was brought on board, there already existed a build of the game that had more levels and weapons than the PC version, and all she had to do was optimize it. In truth, none of that extra content existed, and Art Data expected her to add all that stuff on her own in two months. That wasn't happening.
Considering how much worse the end result could have been, Heineman did a pretty spectacular job. On a positive note, since she couldn't port the music driver, she got a band to redo the entire soundtrack, which surprisingly wound up working for the best. But you can judge the quality of her work yourself — click the link above to get the source code and give it a quick look.