Generated by SassMeister.com, the Sass playground.

SassMeister-input.scss

// Sass v3.2.3

$menu-text-color: #333;
$menu-bg-color: #ccc;


#navbar {
    width: 80%;
    height: 23px;
    
    ul {list-style:none;} 

li {float:left; 
        a {
            font-weight: bold;
            color: $menu-text-color;
            background-color: $menu-bg-color;
        }
        
        a.current-item {
            color: invert($menu-text-color);
            background-color: invert($menu-bg-color);
            }

    }

}

SassMeister-output.css

#navbar {
  width: 80%;
  height: 23px;
}
#navbar ul {
  list-style: none;
}
#navbar li {
  float: left;
}
#navbar li a {
  font-weight: bold;
  color: #333333;
  background-color: #cccccc;
}
#navbar li a.current-item {
  color: #cccccc;
  background-color: #333333;
}