Sinclair ZX80 / ZX81 / Z88 Forums

Hi all,

I have finished porting my 3D ZX Spectrum game, Cosmic Payback, to the 16K ZX81. You control a spherical pod, bouncing through space and retrieving all of the flashing tiles (which represent gold).

Please find attached to this post some screenshots and, more importantly, the ZIP folder containing the tape in P format and the game manual. This game uses a pseudo hi-res technique, and is therefore capable of running on any stock ZX81, with any RAM pack of at least 16K capacity.

I hope you enjoy playing it as much as I've enjoyed writing it

Thanks,
John

(corresponding thread on Spectrum Computing: https://spectrumcomputing.co.uk/forums/ ... hp?t=13275)

Excellent stuff! Is this destined for a physical cassette release by any chance?

Fruitcake wrote: ↑Sun Mar 30, 2025 1:22 pm Excellent stuff! Is this destined for a physical cassette release by any chance?

That's exactly what I was going to ask. Hope so.

Thanks for your interest! I hadn't considered a physical cassette release, but if there's enough enthusiasm for it, and a publisher interested in taking it on, then I'd be more than happy to do so.

That's brilliant. Maybe talk to Cronosoft?

Superb!!!
I have enjoyed very much this awesome game on my Speccy, to be honest I was never expecting to see such a little miracle squeezed into 16k on the Zeddy!! What a pleasant surprise and how nicely done!!!

Congratulations for your work and thank you for sharing!

Minor typo:

I have found the cause of the star rendering bug displayed on certain machines - it was an oversight in the star video driver, reading back from the $c000 to $ffff region and expecting it to be a mirror of the 16K RAM. This meant that the data read to set the I-page for the next row of stars was wrong on machines with extra RAM mapped in this region.

I have now produced a patched version of the game with a fix for this bug, and a correction for the minor typo spotted by sboisvert. You can find a download for this new file in the first post.