div.main { background-image: linear-gradient(#000, #fff) }
.collapser::before,
.collapser::-moz-before,
.collapser::-webkit-before {
    content: "»";
    font-size: 1.2em;
    margin-right: .2em;
    -moz-transition-property: -moz-transform;
    -moz-transition-duration: .2s;
    -moz-transform-origin: center 60%;
}
.collapser.expanded::before,
.collapser.expanded::-moz-before,
.collapser.expanded::-webkit-before { -moz-transform: rotate(90deg) }
.collapser + * {
    height: 0;
    overflow: hidden;
    -moz-transition-property: height;
    -moz-transition-duration: .3s;
}
.collapser.expanded + * { height: auto }