纯css只有四个角有边框的样式

效果如图：

 .card-wrap {
            width: 33%;
            height: 100%;
            box-shadow: 0px 0px 12px 1px #003ba26b inset;
            background: linear-gradient(to left, #196aa8, #196aa8) left top
                no-repeat,
              linear-gradient(to bottom, #196aa8, #196aa8) left top no-repeat,
              linear-gradient(to left, #196aa8, #196aa8) right top no-repeat,
              linear-gradient(to bottom, #196aa8, #196aa8) right top no-repeat,
              linear-gradient(to left, #196aa8, #196aa8) left bottom no-repeat,
              linear-gradient(to bottom, #196aa8, #196aa8) left bottom no-repeat,
              linear-gradient(to left, #196aa8, #196aa8) right bottom no-repeat,
              linear-gradient(to left, #196aa8, #196aa8) right bottom no-repeat;
            background-size: 1px 8px, 8px 1px, 1px 8px, 8px 1px；
          }