Always happy to answer any questions!
The original was first of all an old mobile game, I think. I was aware of it cos I know Pascal, I'd seen his games many times, though I'd never played this one. It was pretty clear from playing the first level that it would be fine, (with some restrictions on the number of sprites at once)
Actually I hadn't played it all the way through before starting the conversion. I wasn't really aware of all of the bosses. Thankfully none of them were too bad for converting. I guess I'd just have changed them to fit though if they proved difficult to do.