Re the fact that it appears to be joystick-only, may I suggest to support keyboard?
If you do not want to invest in a key redefine feature, maybe you’d prefer to do like I did in Just Get 9: define several keys for each use so that whatever their habits the player quickly find something that just works.
Details on "Any-setup keys": so every player can play your game, whatever their CPC or emulator - General - CPCWiki.