Typst is a re-flowable document description language; TeX spends more computation on the One True text justification and hyphenation paragraph builder. PDF has

Typst is a re-flowable document description language; TeX spends more computation on the One True text justification and hyphenation paragraph builder. PDF has recently implemented a limited reflow feature by marking up text elements with metadata tags originally introduced to add accessibility features, hints for text to speech... Meanwhile, Amazon has moved new books and user-submitted documents from its own Kindle format to ePub. ePub is the e-book standard format that extends a subset of HTML. Web browser teams have been hurling themselves against the walls of nearly-intractable layout cases for decades now. We take it for granted: on your Kindle e-ink reader, change the font size. Boom: the whole book has to re-compute its layout. Typst is far more computationally efficient, even elegant, but as yet it can't flow text around embedded sidebars or images.