Example of @media bubbling in sass

sass-media-mixins.sass

// media query module
// use: responsive style blocks output to @content
=tablet-portrait
    @media screen and (min-width: 30em)
        @content
=retina
    @media screen and (-webkit-min-device-pixel-ratio: 2)
        @content

// selector
#header
    color $funkypurple
    +tablet-portrait
        color $nofunkpurple
    +retina
        background url(../images/[email protected])