ant-design/style/components/button.less

@import "../mixins/index";
@btnPrefixClass: ~"@{css-prefix}btn";

// Button styles
// -----------------------------
.@{btnPrefixClass} {
  .btn;
  .btn-default;

  &-primary {
    .btn-primary;

    .@{btnPrefixClass}-group &:not(:first-child):not(:last-child) {
      border-right-color: @btn-group-border;
      border-left-color: @btn-group-border;
    }

    .@{btnPrefixClass}-group &:first-child {
      &:not(:last-child) {
        border-right-color: @btn-group-border;
      }
    }

    .@{btnPrefixClass}-group &:last-child:not(:first-child) {
      border-left-color: @btn-group-border;
    }

    .@{btnPrefixClass}-group & + .@{btnPrefixClass} {
      border-left-color: @btn-group-border;
    }
  }

  &-ghost {
    .btn-ghost;
  }

  &-circle, &-circle-outline {
    .btn-circle(@btnPrefixClass);
  }

  &-circle-outline {
    .btn-circle-outline;
  }

  &-menu {
    > .@{iconfont-css-prefix} {
      font-size: @font-size-base;
      font-size: ~"10px \9"; // ie8-9
      .scale(0.83);

      :root & {
        font-size: @font-size-base; // reset ie9 and above
      }
    }
  }

  &-group {
    .btn-group(@btnPrefixClass);
  }
}