a.sm2_button {
 position:relative;
 display:inline-block; /* If you worry about old browser bugs, Firefox 2 might not like this and may need -moz-inline-box instead. :D */
 width:50px;
 height:50px;
 text-indent:-9999px; /* don't show link text */
 overflow:hidden; /* don't draw inner link text */
 vertical-align:top;
 /* and, a bit of round-ness for the cool browsers. */
 /* weird IE 6/7 display fixes, and/or I'm doing it wrong */
 *text-indent:0px;
 *line-height:99em;
 *vertical-align: top;
 background-size: 50px 50px;
}

a.sm2_button:focus {
 outline:none; /* maybe evil, but don't show the slight border outline on focus. */
}

a.sm2_button,
a.sm2_button.sm2_paused:hover {
 background-image:url('/images/play.svg');
 background-repeat:no-repeat;
 background-position:0px 0px;
}

a.sm2_button:hover,
a.sm2_button.sm2_playing,
a.sm2_button.sm2_playing:hover {

}

a.sm2_button.sm2_playing,
a.sm2_button.sm2_playing:hover {
 background-image:url('/images/stop.svg');
  background-repeat:no-repeat;
 background-position:0px 0px;
}

a.sm2_button.sm2_paused {
background-image:url('/images/play.svg');
 background-repeat:no-repeat;
 background-position:0px 0px;
}

a.sm2_button.sm2_paused:hover {
opacity:1;
}