html - 在 CSS 中解开三 Angular 形的 secret

Question

谁能解释一下当 CSS 宽度和高度设置为 0 时它是如何形成一个三 Angular 形的。

.arrow-up {
  width: 0; 
  height: 0; 
  border-left: 5px solid transparent;
  border-right: 5px solid transparent;
  border-bottom: 5px solid black;
}

.arrow-down {
  width: 0; 
  height: 0; 
  border-left: 20px solid transparent;
  border-right: 20px solid transparent;
  border-top: 20px solid #f00;
}

.arrow-right {
  width: 0; 
  height: 0; 
  border-top: 60px solid transparent;
  border-bottom: 60px solid transparent;
  border-left: 60px solid green;
}

.arrow-left {
  width: 0; 
  height: 0; 
  border-top: 10px solid transparent;
  border-bottom: 10px solid transparent;
  border-right:10px solid blue; 
}

<div class="arrow-up"></div>
<div class="arrow-down"></div>
<div class="arrow-left"></div>
<div class="arrow-right"></div>

Answer 1

这只是一个聪明的CSS Trick , 显示在 CSS 技巧上。

It’s basicly like a giant 3D border-corner. (when the left and top border-color are different the edge is diagonal, that’s being used to make this triangle).