SASS responsive mixin (bootstrap breakpoints)

sass-responsive-mixin.scss

/**
 * Responsive mixin. The media breakpoints are as defined
 * in the twitter bootstrap framework:
 *
 * - phone
 * - tablet-portrait
 * - tablet-landscape-desktop
 * - large-desktop
 *
 * Additional parameters for tagetting retina and non-retina
 * devices
 *
 * - retina
 * - non-retina
 *
 * Moreover, a specific value in px can be passed which is
 * used to generate a max-width media query.
 */
@mixin respond-to($media) {
    /* Landscape phones and down */
    @if $media == phone {
        @media (max-width: 480px) { @content; }
    }
    /* Landscape phone to portrait tablet */
    @else if $media == tablet-portrait {
        @media (max-width: 767px) {@content; }
    }
    /* Portrait tablet to landscape and desktop */
    @else if $media == tablet-landscape-desktop {
        @media (min-width: 768px) and (max-width: 979px) { @content; }
    }
    /* Large desktop */
    @else if $media == large-desktop {
        @media (min-width: 1200px) { @content; }
    }
    // Non-Retina
    @else if $media == non-retina {
        @media screen and (-webkit-max-device-pixel-ratio: 1) { @content; }
    }
    // Retina Only
    @else if $media == retina {
        @media screen and (-webkit-min-device-pixel-ratio: 2) { @content; }
    }
    // Specific max width
    @else {
        @media only screen and (max-width: #{$media}px) { @content; }
    }
}