paper-gtk-theme/Paper/gtk-3.18/widgets/_level-bars.scss

/*************
 * Level Bar *
 *************/

%fill-block {
  border-radius:3px;
  margin: 2px;
  background-color: $selected_bg_color;
  border:1px solid;
  border-color: if($variant == 'light', $selected_borders_color, $borders_color);
  box-shadow:inset 0 1px 0 0 $top_highlight;

  &.low,
  &.level-low {
    background-color: $red;
    border-color: if($variant == 'light', darken($red, 10%), $borders_color);
    box-shadow:inset 0 1px 0 0 $top_highlight;
  }

  &.high,
  &.level-high {
    background-color: $green;
    border-color: if($variant == 'light', darken($green, 10%), $borders_color);
    box-shadow:inset 0 1px 0 0 $top_highlight;
  }

  &.full,
  &.level-full {
    background-color: $selected_bg_color;
    border-color: if($variant == 'light', $selected_borders_color, $borders_color);
    box-shadow:inset 0 1px 0 0 $top_highlight;
  }

  &.empty,
  &.empty-fill-block,
  &.level-empty {
    background-color: transparentize(black, 0.9);
    border-color: $borders_color;
    box-shadow: 0 1px 0 0 $bottom_highlight;
  }
}

GtkLevelBar {
  -GtkLevelBar-min-block-width: 32px;
  -GtkLevelBar-min-block-height: 6px;
}

GtkLevelBar.vertical {
  -GtkLevelBar-min-block-width: 6px;
  -GtkLevelBar-min-block-height: 32px;
}

.level-bar {
  border-radius: 2px;
  padding: 2px;

  // Trough - has no style
  &.trough {
    background-color: transparent;
    border:none;
    margin: 2px;
  }

  // Fill block
  &.fill-block { 
    @extend %fill-block;
  }

  // Continuous
  .indicator-continuous {
    &.fill-block {
      @extend %fill-block;
    }
  }

  // Discrete  
  &.horizontal.indicator-discrete.fill-block { margin: 0 1px; }
  &.horizontal.discrete block { margin: 0 1px; }

  &.vertical.indicator-discrete.fill-block { margin: 1px 0; }
  &.vertical.discrete block { margin: 1px 0; }
}