@Kimimaru: Many thanks.
@Tortuga: Of all people I'd expect you to love Amazing Mirror, being the Metroidvania that it is. And for how much you love sequence-breaking. There's basically nothing stopping you from taking on any boss you want in any order you please, and the only progress you need to know about is how many of 'em you've beaten, and the whole treasure collection shebang.
I hear speedruns take a long time, around an hour maybe
100%ing it, however, is hell. But I done it.