Not sure I will be able to join and create something for C64 but would love to.

Before I will start thinking about it though, a quick one as the abbreviations rule is a little bit confusing for me, especially that C64 expands all abbreviations when listing a code. So, does the following example fits in the 72 characters with abbreviations allowed and even without space character after a line number?

5v=53280:pOv,0:pOv+1,0:?"this code takes 72 characters only per line!!!"

Just asking as I got it wrong when submitting my first 10-liner ever game for the Basic 10Liner competition a few months ago in the PUR-80 category. I actually did a "SUPER" or "CLEAN" PUR-80 as my code was fitting in 80 characters per line without abbreviations :D. A lot of sweat but was still worth it :).