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This is a 4k for the good old Sinclair ZX81 with 1k of RAM - therefore a 5 part 4k :-) Wave files are included in the package for those with a real machine (remember to remove your rampack, it will not work with it). Will also probably not run on any emulator other than the one provided (at least I don't know any emulator that runs it properly, if you find one please tell me)

Look at the source code :-) More seriously: in the emulator, hit j, shift-p, shift-p (should read LOAD "" in basic). Press enter to start the loader (fancy bars on screen). The hit F1, the first part will load. When the strange loading pattern is back, hit F2, then F3, and so on and finally F5 for the last part.

viznut: As far as I know, this is the first demo for the unexpanded ZX81, yeah. I actually know only one other multipart demo (in the sense of a program showing a series of effects, rather than illustrating one single technical stunt); it is 25th anniversary by Bodo Wenzel (http://members.fortunecity.de/bodo4all/zx/25thanni.htm#).
For the sound, the ZX81 actually has the audio and video outputs wired together - the black and white stripes shown on TV are the audio signal :-) It is therefore highly unlikely that we'll ever see something that is both good-looking and good-sounding at the same time.

It does run very nicely on a real machine - and was shown running on real hardware at quite a few public events since its release. For example, here is a photograph of the demo running at the Imaging the Future event in 2004 (the audio data is read from that crappy audio CD player lying on the TV, this is just much more reliable than those crappy tapes). Just do not forget to remove any rampacks or other useless extensions before attempting to load this...

Hi-res is full software, as usual, since the ZX81 does not really have any display hardware :-) Resolutions depend on the displayed effects: the 'copper' bars are 256x192, the first part scroller is more like 320, although the single clock cycle shift used in the shadow means that pixels are active for almost all 414 columns available on a single scanline. The octahedra are rendered to a much smaller framebuffer, which is then repeated three times and moved around. The final part does 192x96, with every second scanline used for decompressing the one coming after that since there is not enough memory for storing the whole image :-) The starfield technically doesn't even have a resolution, since it is just single-byte framebuffers (i.e. 8 pixels) that are placed using a function that takes the number of clock cycles it should take to execute as a parameter. The ZX81 is really a wonderful machine for playing around with synchronous programming due to its lack of any really useful hardware - the processor essentially drives the electron beam in real time through a shift register.

I don't have the slightest idea what that fixed version is about - I only ever released the one you get in the original download. Maybe it is the one that Bodo Wenzel repacked for 16k ZX81, maybe not... Whatever... All required wav files are in the original download. There are no .p files since the intro uses a speedloader (Yes! Really!). The speedloader is actually necessary since it fits in 54 bytes - less than what would be taken by the ROM variables if I used the ROM loader (hehe, not only 10 times faster than original loading speed, but even a precious byte saver :-) ). The tool to create wav files from the binaries/source is also in the original package. The only other version I have is a private version that was used for various shows that runs in a loop (i.e. a one hour wave file that loops the demo for the duration of the CD)

OK, that file is the version that Bodo Wenzel modified - not my original. My original is a 5-part intro for 1k ZX81, and it does not (and I really mean not) support rampacks or extensions of any kind. It will only run on original european 1k ZX81 machines. The hi-res modification is only required for rampacks, without a rampack the weird refresh-read wiring is already present on the mainboard :-) - i.e. the 1k machine is already hi-res enabled by default.

Try this for a video http://www.youtube.com/watch?v=ztkQMjdPtuQ. Not my recording, but the first I found where someone actually had the original version running on the real machine!