gnome-shell/data/theme/gnome-shell-sass/widgets/_screenshot.scss

// Screenshot UI
.icon-label-button-container {
  spacing: $base_padding;
  @extend %caption;

  StIcon { icon-size: 32px;}
}

$screenshot_ui_panel_padding: $base_padding*3;
$screenshot_ui_shot_cast_margin: 21px;
$screenshot_ui_panel_border_radius: $modal_radius + $screenshot_ui_shot_cast_margin;
$screenshot_ui_shot_cast_spacing: 3px;

$screenshot_ui_button_red: $error_color;

.screenshot-ui-panel {
  @extend %osd_panel;
  border-radius: $screenshot_ui_panel_border_radius;
  padding: $screenshot_ui_panel_padding;
  // Reduce the bottom padding a little to accommodate the large capture button.
  padding-bottom: $screenshot_ui_panel_padding - 6px;
  margin-bottom: 4em;
  spacing: $base_padding * 2;
}

.screenshot-ui-close-button {
  @extend .window-close; // copy window close button
  padding: $base_padding !important; // but with more padding
  margin-top: 12px;
  box-shadow: 0 2px 4px 0 $shadow_color;
  &.left { margin-left: 12px;}
  &.right { margin-right: 12px;}
}

.screenshot-ui-type-button {
  @extend %osd_button_flat;
  min-width: 48px;
  padding: $base_padding * 2 $base_padding * 3 !important;
  border-radius: $screenshot_ui_panel_border_radius - $screenshot_ui_panel_padding;
}

.screenshot-ui-capture-button {
  width: 36px;
  height: 36px;
  border-radius: 99px;
  border: 4px $osd_fg_color;
  padding: 4px;

  .screenshot-ui-capture-button-circle {
    background-color: $osd_fg_color;
    transition-duration: 200ms;
    &:hover, &:focus { background-color: $hover_bg_color;}
    border-radius: 99px;
  }

  &:hover, &:focus {
    .screenshot-ui-capture-button-circle {
      background-color: darken($osd_fg_color, 15%);
    }
  }

  &:active {
    .screenshot-ui-capture-button-circle {
      background-color: darken($osd_fg_color, 50%);
    }
  }

  &:cast {
    .screenshot-ui-capture-button-circle {
      background-color: $screenshot_ui_button_red;
    }
    &:hover, &:focus {
      .screenshot-ui-capture-button-circle {
        background-color: lighten($screenshot_ui_button_red, 5%);
      }
    }
    &:active {
      .screenshot-ui-capture-button-circle {
        background-color: darken($screenshot_ui_button_red, 7%);
      }
    }
  }
}

.screenshot-ui-shot-cast-container {
  background-color: transparentize($osd_fg_color,0.9);
  border-radius: $modal_radius;
  padding: $screenshot_ui_shot_cast_spacing;
  spacing: $screenshot_ui_shot_cast_spacing;

  &:ltr { margin-left: $screenshot_ui_shot_cast_margin - $screenshot_ui_panel_padding;}
  &:rtl { margin-right: $screenshot_ui_shot_cast_margin - $screenshot_ui_panel_padding;}
}

.screenshot-ui-shot-cast-button {
  padding: $base_padding $base_padding*2;
  background-color: transparent;
  &:hover, &:focus { background-color: transparentize($osd_fg_color, 0.8);}
  &:active { background-color: transparentize($osd_fg_color, .5);}
  &:checked { background-color: $osd_fg_color; color: $osd_bg_color;}
  &:insensitive { color: transparentize($osd_fg_color, 0.5);}

  border-radius: $modal_radius - $screenshot_ui_shot_cast_spacing;

  StIcon { icon-size: $base_icon_size;}
}

.screenshot-ui-show-pointer-button {
  @extend %osd_button_flat;
  border-radius: 99px;
  padding: $base_padding * 2 !important;
  StIcon { icon-size: $base_icon_size;}
}

.screenshot-ui-area-indicator-shade {
  background-color: rgba(0,0,0,.3);
}

.screenshot-ui-area-selector {
  .screenshot-ui-area-indicator-shade {
    background-color: rgba(0,0,0,.5);
  }

  .screenshot-ui-area-indicator-selection {
    border: 2px white;
  }
}

.screenshot-ui-area-selector-handle {
  border-radius: 99px;
  background-color: white;
  box-shadow: 0 1px 3px 2px $shadow_color;
  width: 24px;
  height: 24px;
}

.screenshot-ui-window-selector {
  background-color: $system_bg_color;

  .screenshot-ui-window-selector-window-container {
    margin: 100px;
  }

  &:primary-monitor {
    .screenshot-ui-window-selector-window-container {
      // Make some room for the panel.
      margin-bottom: 200px;
    }
  }
}

.screenshot-ui-window-selector-window-border {
  transition-duration: 200ms;
  border-radius: $modal_radius;
  border: 6px transparent;
}

.screenshot-ui-window-selector-check {
  transition-duration: 200ms;
  color: transparent;
  border-radius: 99px;
  border-width: 12px;
  icon-size: 24px;
}

.screenshot-ui-window-selector-window {
  &:hover {
    .screenshot-ui-window-selector-window-border {
      border-color: darken($selected_bg_color, 15%);
    }
  }
  &:checked {
    .screenshot-ui-window-selector-window-border {
      border-color: $selected_bg_color;
      background-color: transparentize($selected_bg_color, 0.8);
    }

    .screenshot-ui-window-selector-check {
      color: $selected_fg_color;
      background-color: $selected_bg_color;
    }
  }
}

.screenshot-ui-screen-selector {
  transition-duration: 200ms;
  background-color: rgba(0,0,0,.5);

  &:hover { background-color: rgba(0,0,0,.3);}
  &:active { background-color: rgba(0,0,0,.7);}
  &:checked {
    background-color: transparent;
    border: 2px white;
  }
}

.screenshot-ui-tooltip {
  @extend %tooltip;
  text-align: center;
  -y-offset: 24px;
}