5. less

less is more than css

npm install -g less

lessc <file>.less <file>.css
lessc -x <file>.less   // output the compiled CSS

用法:

// Variables
@color: #4D926F;
@height: `document.body.clientHeight`;

@color: color(`window.colors.baseColor`);
@darkcolor: darken(@color, 10%);

// Mixins
.rounded-corners (@radius: 5px) {
   ...
}

// Nested Rules
#header {
  p { font-size: 12px;
    a { text-decoration: none;
      &:hover { border-width: 1px }   // #header p a:hover
    }
  }
}

// Functions & Operations
(@base-color * 3)
desaturate(@red, 10%)

//其他
~"<string>"   // Escaping