Thanks for your kind feedback guys. I'm looking at developing it in chapters so it doesn't blow out into an unmanageably large project as can easily happen with games when working solo.
I envisage that each chapter could be totally unique in terms of gameplay mechanics, story, audio systems, colour schemes, etc, but I'll see how time goes and if collaborators emerge.
I should add also that Starquake by Stephen Crow was a big influence :)