[RbnJrg]

Originally Posted by Lukusaukko

Works in Editor, though, which is a bit strange... Anyway, thanks to all who contributed, I've got it sorted now. Also, note to self: don't try anything too fancy...

Why? Calibre Viewer is a great piece of software, based on one of the latest versions of webkit, and supports the epub3 protocol very well. So, anything "too fancy" also will work on Calibre Viewer. Your issue is that you employed the wrong property; you used "first-line" when you should use "first-child" or "firts-of-type" with the sibling combinator "~". For example:

div.indented {
  padding: 1em 1.5em 1em 2em;
}

div.indented p {
  margin: 0.5em 0 0.5em 1.5em;
  line-height: 1.2em;
}

div.indented p:first-child {
  text-indent: -1.5em;
}

div.indented p:first-child ~ p {
  text-indent: -1.5em;
}

Watch the epub I attach. And here you can watch how it looks on Calibre Viewer and also on Sigil:



Of course, all that "fancy code" (is not fancy, is trivial) is not neccesary because the effect can be achieved with less code and simpler (as I wrote in my previous post). But I include all this css so you can be sure that Calibre Viewer will support advanced css properties and selectors.