How it works
The stylesheet is scanned character by character, tracking nesting depth
through every { and }. Each declaration and selector is re-printed on
its own line with two spaces of indentation per level, which also handles
nested at-rules like @media correctly.
What gets removed
Comments (/* ... */) are stripped, and repeated whitespace inside a
declaration is collapsed to a single space. Property values, selectors,
and the cascade itself are left completely untouched.
Common uses
Making a minified stylesheet from a build tool readable for debugging, or cleaning up CSS copied from a source that stripped all the formatting.