CleverCSS is a small markup language for CSS inspired by Python that can be used to build a style sheet in a clean and structured way. In many ways it's cleaner and more powerful than CSS2 is.

The most obvious difference to CSS is the syntax: it is indentation based and not flat. While this is obviously against the Python Zen, it's nonetheless a good idea for structural styles.

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This works like normal css @imports, but expects a ccss file, which is then parsed, allowing cross-sheet variables

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Sometimes CleverCSS is a bit too clever for its own good and you just want to pass something directly to CSS. For instance, functions that aren't rgb() or url() need to be escaped. Added is a simple new backtick-surrounded string format that will be passed verbatim without further processing. Example:

.gradient:
    background: `-moz-linear-gradient(...)`

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Commonly in CSS, you'll have an image of all your UI elements, and then use background positioning to extract a part of that image. CleverCSS helps you with this, via the spritemap(fn) call. For example:

ui = spritemap('ui.sprites')
some_button = $ui.sprite('some_button.png')
other_button = $ui.sprite('other_button.png')

div.some_button:
    background: $some_button

div.other_button:
    background: $other_button
    width: $other_button.width()
    height: $other_button.height()

There is currently only partial mixin support -- arguments are not yet implemented. But they will be...sometime soon. Anyway, the syntax for a macro is [currently] pretty pythonic:

def macro:
  color: red
  border-width: 5px - 1px

body:
  $macro

This syntax may change, though, b/c conceivably "def macro:blah" could refer to the CSS "def macro { blah }", so there is some inconsistent magic going in.

To get an idea of how CleverCSS works you can see a small example below. Note the indentation based syntax and how you can nest rules:

ul#comments, ol#comments:
  margin: 0
  padding: 0

  li:
    padding: 0.4em
    margin: 0.8em 0 0.8em

    h3:
      font-size: 1.2em
    p:
      padding: 0.3em
    p.meta:
      text-align: right
      color: #ddd

Of course you can do the very same in CSS, but because of its flat nature the code would look more verbose. The following piece of code is the CleverCSS output of the above file:

ul#comments,
ol#comments {
  margin: 0;
  padding: 0;
}

ul#comments li,
ol#comments li {
  padding: 0.4em;
  margin: 0.8em 0 0.8em;
}

ul#comments li h3,
ol#comments li h3 {
  font-size: 1.2em;
}

ul#comments li p,
ol#comments li p {
  padding: 0.3em;
}

ul#comments li p.meta,
ol#comments li p.meta {
  text-align: right;
  color: #dddddd;
}

But that's only a small example of what you can do with CleverCSS. Have a look at the following documentation of CleverCSS for more details.