// Opacity
//
// $level - The opacity level, a number ranging from 0 to 1
//
// Usage:
//
//   @include opacity(0.8);
//
@mixin opacity($level: 1) {
  $ms-level: $level*100;
  -ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=#{$ms-level})";
  filter: alpha(opacity=#{$ms-level});
  opacity: #{$level};
}