Its one of 3 games in development for 2013 for the ZX81.
The first one available is Shifted (out in apeldoorn). A great fun and addictive game but that isnt as cool a screenshot as this one.
The third one is a boxing game, also with nice graphics (there is a bunch of large animated characters in there, so it will be a big squeeze getting it into the available space).
It looks good, I definitely want it both on tape and binary

Does it have ZXpand/ZonX sound support ?
I have been playing with a AY-3-8910 emulator addon (ported from a piece of code for the Parallax Propellor!) on my NXP81 and it already gives out some sounds (both with a demo and Mayhem/Avalanche/Stairrunner/Down).
Dennis (DDW) tested your ZX81 games with a real ZONX and it gave no sound.. Seems there was an IO address mixup on the real ZonX (0x0F/0x1F and 0x0C/0x1C) It has something to do with A4 not properly connected on some ZonX boxes. I had to adjust the emulator to also react on both variations.
If all is well we will attend Apeldoorn with a bunch from Steenwijk

P.S. do you take the PET game(s) also to Apeldoorn ? (just for fun I tested a 6502 emulator on the mbed and used the PET as example code to see how it would run and the bootup screens already showed up so..)