css样式设置方框右上角小图标

.rem_icon {
        position: absolute;
        width: 0;
        height: 0;
        border-top: 20px solid transparent;
        border-bottom: 20px solid transparent;
        border-left: 30px solid #000000;
        border-radius: 50%;
        transform: translate(0 , -30px) rotate(-40deg);
        text-align: left;
        color: #FFFFFF;
      }
      .rem_icon:after{
        content: '+';
        color: #ffffff;
        position: absolute;
        left: -30px;
        bottom: -13px;
      }

​​这个才是神手的，服​​.