Great job! Just out of interest what tools / framework(s) etc. did you use to build the ZX Spectrum version? Thanks 
PS: well done for keeping a Development log - I keep meaning to do this but never do…!!
Thanks!
The code is written using Microsoft’s VS.Code editor, along with a couple of plug-ins for syntax colouring and counting the t-states of a selected block of code. Everything is then compiled using the Pasmo assembler, which has been updated to support compiling to the memory bank pages required for a 128K game such as this.
The graphics are done in an old version of Photoshop elements (from when it was still pretty close to Photoshop instead of the photo-retouching service it is now). These are output as required for the game code using some basic scripts in Unity. That gives me the flexibility to write whatever I need the output format to be, and use just about any input image format.
Everything is then tested in the Spin emulator.
Thanks a lot Bob for information - I'm glad I asked about this because this is the first time I've heard about using the Pasmo assembler :) http://pasmo.speccy.org Again great job with game. Regards, Steven.