I'm a big fan of Ange Albertini's work with this kind of stuff - https://github.com/corkami/ https://github.com/corkami/ There's a talk called "Funky File Form

I'm a big fan of Ange Albertini's work with this kind of stuff - https://github.com/corkami/ https://github.com/corkami/ There's a talk called "Funky File Formats" but there's (fittingly) multiple versions of it so you're best off searching for it.