I remember going through the original Doom source code after it was released as open source. Although it seemed way over my head, I learned a lot about how wel

I remember going through the original Doom source code after it was released as open source. Although it seemed way over my head, I learned a lot about how well C code can be made to work, even for a complex game (at least at that time). I also got to appreciate John Carmack's coding style/skill even more.