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Comment by VonGuard | Hacker News Reader

Howard is a brilliant programmer. In Yar's Revenge, that fuzzy barrier on the left side of the screen is the graphics code from the program literally reading the game's own code as graphical data, thus creating the crazy static pattern of chaotic colors. Talk about a cool and space saving hack! https://upload.wikimedia.org/wikipedia/en/8/85/A2600_Yars_Re...

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I accidentally produced a similar effect while working on my voxel game engine: https://twitter.com/jmhobrien/status/624133887036424193

Basically, just deferenced a pointer to OpenGL memory that I shouldn't have...

I think all lower-level programmers have done similar mistakes at one time or other. I managed to do it several times while learning assembler on the Atari ST/STE/Falcon :-)

I've done it countless times, and not by accident. Sometimes this is the only way to debug things.

Most BBC Micro games loaded like this: game data would spill into memory mapped video and then dealt with after.

The BBC Micro also allows you to change the address of the video framebuffer. A particularly neat trick was to remap it to 0x0000, so you get to see the OS workspace, stacks, program storage etc. You can watch the bits twiddle in realtime as you do things.

There's another neat hack which would cause the machine to run in slow motion. I don't know how it worked; I can't find any references now. Possibly it overloads the system with interrupts. But under its influence, clearing the screen would take several seconds. These two hacks combined beautifully, letting you see all the details of, e.g., Basic's heap management.

The slow motion thing can be found in BEEBUG, Volume 2 No. 6, p31: http://8bs.com/beebugmags.htm

It does overload the system with interrupts, by making the (normally 100Hz) timer interrupt that the OS uses occur a lot more frequently.

Nice looking game! I hope you saved that code for later levels ..

The Atari: Game Over movie is on Netflix. It'll give people more insight. The guy was an exceptional programmer and good game designer who was dealt a death march with a hard deadline.

Similar trick was used a couple of years later in Revs on the BBC Micro: https://en.wikipedia.org/wiki/Revs_(video_game)

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