如何为(8点星)css形状添加边框？

如何在这个8点星外面添加红色边框？或者有没有人知道的简单的svg解决方案？

IS: 需要:

JS小提琴

HTML

CSS

#star8 {
 border: 3px solid red;
 background: blue; width: 80px;
 height: 80px;
 position: relative;
 -webkit-transform: rotate(20deg);
 -moz-transform: rotate(20deg);
 -ms-transform: rotate(20deg);
 -o-transform: rotate(20eg);
 }
#star8:before {
 content: "";
 position: absolute;
 top: 0;
 left: 0;
 height: 80px;
 width: 80px;
 background: blue;
 -webkit-transform: rotate(135deg);
 -moz-transform: rotate(135deg);
 -ms-transform: rotate(135deg);
 -o-transform: rotate(135deg);
 }

G-Cyr.. 6

你可以使用mix-blend-mode,最后使用另一个伪:DEMO

#star8:after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  height: 80px;
  width: 80px;
  transform: rotate(135deg);
  box-shadow: 0 0 0 3px red;::* a border works too */
  mix-blend-mode:overlay;
}

#star8 {
  margin: 2em;
  border: 3px solid red;
  background: blue;
  width: 80px;
  height: 80px;
  position: relative;
  transform: rotate(20deg);
}

#star8:before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  height: 80px;
  width: 80px;
  background: blue;
  transform: rotate(135deg);
}

#star8:after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  height: 80px;
  width: 80px;
  transform: rotate(135deg);
  box-shadow: 0 0 0 3px red;
  mix-blend-mode:overlay;
}

#star8 {
  margin: 2em;
  border: 3px solid red;
  background: blue;
  width: 80px;
  height: 80px;
  position: relative;
  transform: rotate(20deg);
}

#star8:before {
  content: "";
  position: absolute;
  z-index:-1;
  top: 0;
  left: 0;
  height: 80px;
  width: 80px;
  background: blue;
  transform: rotate(135deg);
  box-shadow: 0 0 0 3px red;
}

#star8:after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  height: 80px;
  width: 80px;
  background: blue;
  transform: rotate(0deg);
}

#star8:after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  height: 80px;
  width: 80px;
  transform: rotate(135deg);
  box-shadow: 0 0 0 3px red;::* a border works too */
  mix-blend-mode:overlay;
}

#star8 {
  margin: 2em;
  border: 3px solid red;
  background: blue;
  width: 80px;
  height: 80px;
  position: relative;
  transform: rotate(20deg);
}

#star8:before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  height: 80px;
  width: 80px;
  background: blue;
  transform: rotate(135deg);
}

#star8:after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  height: 80px;
  width: 80px;
  transform: rotate(135deg);
  box-shadow: 0 0 0 3px red;
  mix-blend-mode:overlay;
}