OK, I've already admitted to getting old so I'm allowed to start reminiscing about my childhood
While I used to spend a lot of the time in the video arcades when I was a kid, it was mostly on Xevious (I was a monster) and never really got into things like Mario or Pac Man.
Nevertheless, this is insanely cool. Somebody has found an old backup tape that contains, amongst other things, the source code for Donkey Kong . What makes this really interesting is that the guy who wrote it participates in the discussion Even better, he has a long article about how it was written and what was happening at Atari at the time.
At its peak DK was about 20K of code, and it had to go on a diet to fit in the 16K cartridge; a lot of the images were compressed (notice that Kong himself is symmetrical). Towards the end I was crunching out only a few bytes a day, and it shipped with maybe a dozen bytes free.
Jeez, that brings back some memories 
I started out on the BBC Micro which was an incredibly powerful machine for its time , especially when compared to the competition (Commodore 64, anyone? Or even worse, VIC 20? ). The operating system and BASIC interpreter were also done quite well (none of those disgusting PEEK's and POKE's so common on the other machines) and I learned an enormous amount and picked up a lot of good habits by studying the ROM's. However, it only had about 8-20K of memory free for programs (depending on which graphics mode you used) and so I also spent a lot of my time squeezing every last byte out of the system .
The Beeb ruled the education market, largely due to the UK government choosing it as the computer they would subsidize as part of their drive to introduce computers into schools. As a result, there was a huge amount of educational software being written for it, which resulted in it also being adopted by schools around the world. One of the most prolific authors was a guy from Melbourne, moonlighting from his teaching gig at Melbourne High, IIRC He did really well for himself (even though his stuff was kinda ordinary) and while I wrote and sold a bit of stuff myself, I rue the fact that I didn't get into a few years earlier (ya know, when I was 7 or 8 ) since I just missed the peak. Coulda been independently wealthy at the age of fifteen
Oh well, I'll just have to wait for Awasu to do it. Sigh...
 If you want to look at it, get it here. There's also a funny 6502R instruction guide in the comments (well, it's funny if you're a 6502R programmer ).
 And especially poignant given that I'm right now going through Awasu getting rid of memory leaks and reducing its memory footprint. As a comparison, the core part of Awasu is about 7000K in size, excluding the common stuff that Microsoft provides (another 2500K) and third-party stuff (another 6700K).
 You could even add a second processor, which was way ahead of its time (especially given that this was a home computer).
 Certain OS features could be turned off, allowing you to then steal the memory used to manage them for your own purposes