Interesting game. However, I agree with the other comment here – a tape file is badly needed. ESPECIALLY given that this is a paid-for game, it really MUST be supplied in a better form than just a snapshot. That's so half-hearted. (And .SNA isn't even the best snapshot format: it's wasteful. .Z80 format does the same thing but uses a smaller file size and also supports 128K snaps.) This game NEEDS to be supplied as a .TAP file, and ideally as a .TZX file as well. The .TAP file format is best – especially for regular loaders (i.e. non-turbo loaders) – because it works with EVERYTHING, including loading into real machines. If you want to use a fancy loader, supply a .TZX file as well. (But please note that the new ZX Spectrum Next currently can't handle .TZX files, which is one reason why a .TAP is so important: it's absolutely the best option on the Next.) If you need to have a loading screen designed, I recommend approaching Andy Green, who does superb work (search for Andy Green Pixel Art on Facebook).
Interesting points! The file is currently in .sna format because that's all I originally had to work with. A tape file will be in the works for a probable cassette release :)
Meanwhile the loading screen was recently completed based on what I had left of the original screen art from 1988, and is included in the latest .sna update that just went up!