Thanks for the words of encouragement everyone! I hope to get some early previews uploaded soon. I'm intending to get the title and game intro completed first and I'm going to redo the software sprite routine used for the many enemy sprites on each level. The main Bub and Bob sprites are made from a combination of character "software sprites" and Player overlays. the colours are commonly on each level so I should be able to keep the correct change of colour scheme on each level or perhaps at worst one colour register will be the same throughout but I can work with that nevertheless.
I thought that this would be an ideal game to bring to the A8. It's certainly possible. The screen stays static during gameplay so a nice Dlist routine shouldn't prove too difficult. It's a popular with many people as well. I've certainly played it to it's conclusion in the past
It will be nice when the maps section of G2F is completed as this would make the level construction and character set handling much nicer to work out. I'm looking forward to this feature being completed.
here's a quick gif anim of the game intro that I'm intending to work out at the moment. I don't remember the bubble effect being recreated in any of the other platforms conversion.
I bet the demo coders will recognise the maths used here!