I am the author of Cross-Lib, which is a universal C library meant to be used to write games that can be compiled for about 200 different computers, consoles, arcade boards, scientific calculators, hand-held consoles, hacked toyes, etc...
I have written a few games with it and I can compile them for the ZX81.
You can read about Cross-Lib at:
I have made an experimental ZX81 32K WRX version of the latest game Cross Snake (a Nibbler/Snake clone with many new game elements).
Game play: Avoid starving and losing energy(eat apples), avoid hitting your head against mines or your own body.
Optionally collect rings and $ items to unlock new special items and secrets.
The games has 32 levels (+1 secret level) and has 50 secrets to discover.
The binary is available at:
https://github.com/Fabrizio-Caruso/CROS ... _32k_wrx.P