// Panels

.panel-variant(@border; @heading-text-color; @heading-bg-color; @heading-border) {
  border-color: @border;

  & > .panel-heading {
    color: @heading-text-color;
    background-color: @heading-bg-color;
    border-color: @heading-border;

    + .panel-collapse > .panel-body {
      border-top-color: @border;
    }
    .badge {
      color: @heading-bg-color;
      background-color: @heading-text-color;
    }
  }
  & > .panel-footer {
    + .panel-collapse > .panel-body {
      border-bottom-color: @border;
    }
  }
}

// Panels

.panel-variant(@border; @heading-text-color; @heading-bg-color; @heading-border) {
  border-color: @border;

  & > .panel-heading {
    color: @heading-text-color;
    background-color: @heading-bg-color;
    border-color: @heading-border;

    &.clickable {
      cursor: pointer;
      transition: background-color 300ms ease;

      &:hover {
        background-color: darken(@heading-bg-color, 5%);
      }
    }

    + .panel-collapse > .panel-body {
      border-top-color: @border;
    }
    .badge {
      color: @heading-bg-color;
      background-color: @heading-text-color;
    }
  }
  & > .panel-footer {
    + .panel-collapse > .panel-body {
      border-bottom-color: @border;
    }
  }
}

Change panel mixin to include a 'clickable' class for panel headers
Change panel mixin to include a 'clickable' class for panel headers
