I'm currently writing a book, and I'd like some of the sections to be clearly marked as "difficult" or "optional". Not only sections, but also exercises (I'm using the
exercise package) and theorems (that I am defining with
amsthm)). Something that would work for arbitrary sectioning levels, environments, etc would be great...
edit: I think I should have also said -- I'd like something like a star at the margin, close to the section/theorem/etc, and, if it's a section or chapter, then there should be a star before it in the text and at the table of contents:
1 Introduction 1.1 blah 2.3 blah 2 Some Chapter 2.1 blah * 2.2 this is an optional section 2.3 blah blah
edit: it would be nice if the star (or a configurable symbol of course) was placed before the section number.