• 缝边效果

.box{
  width:400px;
  height: 200px;
  margin: 20px;
  outline: 1px white dashed;
  outline-offset:-10px;
  background:#f90;
}

微信截图_20221126150627.png

• 蚂蚁线

.box{
  width:400px;
  height: 200px;
  margin: 100px;
  border: 2px solid transparent;
  background: linear-gradient(white,white) padding-box,repeating-linear-gradient(-45deg, black 0, black 25%, white 0, white 50%) 0/.6em .6em;
  animation:ants 12s linear infinite;
}
@keyframes ants{100%{background-position:100%;}}

还有一种蚂蚁线

.box {
  width: 300px;
  height: 200px;
  background: linear-gradient(90deg, #03a9f4 50%, transparent 0) repeat-x,
    linear-gradient(90deg, #03a9f4 50%, transparent 0) repeat-x,
    linear-gradient(0deg, #03a9f4 50%, transparent 0) repeat-y,
    linear-gradient(0deg, #03a9f4 50%, transparent 0) repeat-y;
  background-size: 8px 1px, 8px 1px, 1px 8px, 1px 8px;
  background-position: 0 0, 0 100%, 0 0, 100% 0;
  animation: linearBox 0.5s infinite linear;
}
@keyframes linearBox {
  100% {
    background-position: 6% 0, -6% 100%, 0 -6%, 100% 6%;
  }
}
@keyframes linearBox {
        100% {
            background-position: 6% 0, -6% 100%, 0 -6%, 100% 6%;
        }
    }

微信截图_20221126151144.png

• 信封边框
  ++ 背景渐变

.box{
  width:400px;
  height: 200px;
  margin: 100px;
   padding:1em;
  border: 1em solid transparent;
  background: linear-gradient(white,white) padding-box,repeating-linear-gradient(-45deg, red 0, red 12.5%, transparent 0, transparent 25%, #58a 0, #58a 37.5%, transparent 0, transparent 50%) 0/5em 5em;
}

++ 边框图片

.box{
  width:400px;
  height: 200px;
  margin: 100px;
    padding:1em;
  border: 1em solid transparent;
  border-image:repeating-linear-gradient(-45deg, red 0, red 1em, transparent 0, transparent 2em, #58a 0, #58a 3em, transparent 0, transparent 4em)  16;
}

微信截图_20221126151532.png

• 脚注效果

.box{
  width:400px;
  height: 200px;
  margin: 100px;
   //由于使用了currentColor，它会根据color属性的变化而自动适应
  padding-top:1em;
  border-top: .2em solid transparent;
  border-image: 100% 0 0 linear-gradient(90deg,currentColor 4em,transparent 0);
}

微信截图_20221126152207.png