@licho as long as you don't mind epubcheck passing (and getting it to run on various devices) the world is your oyster. For actual shippable stuff, I've never used JS, but did create some "choose your path" interactive stories where various options jump you around (pure anchor tags)

@Sascha_Raubal pretty much, yeah. There's also a handy plugin for Sigil: https://github.com/jun-hyung-joon/EpubChecker-sigil - although these days I prefer the command line tool for quick checks.

@Sascha_Raubal yup. the good old trusty https://www.w3.org/publishing/epubcheck/

@akkana Interesting! That page-turn difference seems to point to what @squishymage42 said about dual render pathways for epub vs kepub. Their proprietary format gets the good stuff while regular EPUBS gets sidelined to legacy Adobe render. Crazy.

@squishymage42 The plot thickens!

btw: it actually left scars. that one boot left my wireless headset in a crackly state after reboot into linux. the only thing that fixed it was complete PSU/capacitor drain. jfc