I am very grateful for your comments.
As a matter of fact I immediately implemented your suggestion about highlighting legal moves - and it turned out to be very easy to do. Lots of tedious rule-learning obviated. So great suggestion. I haven't uploaded it yet but will.
I also didn't think about giving the maps names, and certainly technically it would be very easy. It might be somewhat tricky to indicate the nature of the topography of a particular map with a name, if a complex one, but certainly possible, and a name, even if simple, might be easier to remember than a number. I'll think about that one.
I shall have a look into getting the program to let the user know that they "need not adjust their sets": the enemy general is thinking...
As to the difficulty of distinguishing pieces, I genuinely don't know what you mean. I am a blind old geezer but even I can see which piece is which very easily. Maybe I'm just very used to the pieces, or maybe the screen-size is critical: I have a largish computer screen (about 15 1/2 inches I think).