gistfile1.sass

button, a.button
    +border-radius(5px, 5px)
    +box-shadow(0px 1px 1px #999)
    text-align: center
    position: relative
    display: inline-block
    border: none
    font-family: $blueprint-font-family
    font-size: 14px
    color: #333
    text-shadow: 0px 1px 1px #efefef
    
    .background
        +border-radius(5px, 5px)
        +transition-property(all)
        +transition-duration(0.1s)
        +transition-timing-function(ease-in)
        position: absolute
        top: 0
        right: 0
        bottom: 0
        left: 0

    .hover
        opacity: 0
        cursor: pointer

    .active
        +box-shadow(0px 1px 1px #999, 0px 2px 5px #333 inset)
        opacity: 0
        cursor: pointer

    .label
        position: relative
        cursor: pointer

    &:hover
        .hover
            opacity: 1

    &:active
        .active
            opacity: 1