Movements is in.
Finishing this 'stepping-stone', this has been the largest block and I had to clean errors from early blocks too!
Currently movement has no bounds checking, and I think the code could be cleaner.
But that ones done. The next step has to be a kind of cleansing and then adding in the wrapping code and introducing a global co-ordinate system.
Then I can move to a new chapter of stepping stones, that will probably be concerned with timing.