That's a really fantastic idea, but (yes, sorry ;) there are many fonts missing (I use Fantasque Sans Mono), the syntax highlighting theme should be customisabl

That's a really fantastic idea, but (yes, sorry ;) there are many fonts missing (I use Fantasque Sans Mono), the syntax highlighting theme should be customisable (at least a light theme) and the source's language should be changeable. So I always end up using two browser windows of https://www.programmingfonts.org/ https://www.programmingfonts.org/ side-by-side for comparisons.