$panel-background-color: $white !default;
$panel-border-color: rgba($black, .2) !default;
$panel-border-color-fallback: $gray-light !default;
$panel-border-width: 1px !default;
$panel-border-radius: $border-radius !default;

%panel {
  background: $panel-background-color;
  background-clip: padding-box;
  overflow: hidden;
  border-style: solid;
  border-width: $panel-border-width;
  border-color: $panel-border-color-fallback;
  border-color: $panel-border-color;
  border-radius: $panel-border-radius;
}

%panel-top {
  @extend %panel;

  border-style: none none solid;
  border-radius: 0;
}

%panel-right {
  @extend %panel;

  border-style: none none none solid;
  border-radius: 0;
}

%panel-bottom {
  @extend %panel;

  border-style: solid none none;
  border-radius: 0;
}

%panel-left {
  @extend %panel;

  border-style: none solid none none;
  border-radius: 0;
}