如何为CSS绘制的三角形添加渐变效果？

当前实现三角形的代码片段：

.spinner::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  margin: auto;
  width: 0;
  height: 0;
  border-top: 20px solid transparent;
  border-bottom: 20px solid transparent;
  border-left: 27px solid #B76BF0;
  transform: translateX(4px);
  z-index: 0;
}

需要修改以下完整代码来实现渐变效果：

原始完整代码 #

CSS

.spinner {
  -webkit-appearance: none;
  appearance: none;
  border: none;
  padding: 0;
  display: block;
  cursor: pointer;
  position: fixed;
  left: 0;
  top: 0;
  bottom: 0;
  right: 0;
  margin: auto;
  box-sizing: border-box;
  background-clip: padding-box;
  width: 90px;
  height: 90px;
  border-radius: 50%;
  transform-origin: 50% 55%;
  transform: perspective(90px) rotateX(30deg);
  animation: spinner-wiggle 5.2s infinite;
}

.spinner::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  margin: auto;
  width: 0;
  height: 0;
  border-top: 20px solid transparent;
  border-bottom: 20px solid transparent;
  border-left: 27px solid #B76BF0;
  transform: translateX(4px);
  z-index: 0;
}

@keyframes spinner-wiggle {
  30% {
    transform: perspective(90px) rotateX(10deg);
  }

  40% {
    transform: perspective(90px) rotateX(7deg);
  }

  50% {
    transform: perspective(90px) rotateX(10deg);
  }

  60% {
    transform: perspective(90px) rotateX(8deg);
  }
}

.color-circle {
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  margin: auto;
  width: 90px;
  height: 90px;
  transform-origin: 50% 50%;
  background: linear-gradient(100deg, #24A4EA, #379DEB 25%, #B76BF0);
  border-radius: 50%;
  z-index: 0;
  box-shadow: inset 0 24px 18px -10px rgba(0, 0, 140, 0.3),
    inset 0 0 22px -2px rgba(0, 0, 0, 0.4);
  cursor: pointer;
  -webkit-mask-image: radial-gradient(circle, transparent 0 36px, black 36px);
  mask-image: radial-gradient(circle, transparent 0 50px, black 20px);
}

.spinner:hover .color-circle {
  background: -webkit-gradient(linear,
      left top,
      left bottom,
      color-stop(50%, rgba(34, 204, 0, 0.9)),
      color-stop(100%, #55ff00));
  animation: spin 1.7s infinite linear;
}

.color-circle:before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  margin: auto;
  width: 72px;
  height: 72px;
  border-radius: 50%;
  background-color: #353198;
  z-index: 0;
}

@-webkit-keyframes spin {
  0% {
    transform: rotateZ(0deg);
  }

  100% {
    transform: rotateZ(360deg);
  }
}

HTML

<div class=" spinner">
    <span class="color-circle"></span>
</div>

解决方案 #

CSS的border属性无法直接设置渐变背景，我们可以用背景渐变+形状裁剪的方式替代原border实现，得到渐变三角形：

修改.spinner::before的代码如下：

.spinner::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  margin: auto;
  width: 27px; /* 对应原border-left的宽度 */
  height: 40px; /* 对应原border-top + border-bottom的总高度 */
  background: linear-gradient(100deg, #24A4EA, #B76BF0); /* 和color-circle一致的渐变 */
  clip-path: polygon(0 0, 100% 50%, 0 100%); /* 裁剪出向左的三角形 */
  transform: translateX(4px);
  z-index: 0;
}

原理说明：

1. 用矩形元素替代原border绘制：宽度设为原border-left的27px，高度设为上下border的总高度40px（20px+20px）。
2. 给矩形设置需要的渐变背景，这里和.color-circle的渐变保持一致。
3. 通过clip-path: polygon(0 0, 100% 50%, 0 100%)将矩形裁剪成向左的三角形，和原border实现的形状完全匹配。

修改后的完整代码 #

CSS

.spinner {
  -webkit-appearance: none;
  appearance: none;
  border: none;
  padding: 0;
  display: block;
  cursor: pointer;
  position: fixed;
  left: 0;
  top: 0;
  bottom: 0;
  right: 0;
  margin: auto;
  box-sizing: border-box;
  background-clip: padding-box;
  width: 90px;
  height: 90px;
  border-radius: 50%;
  transform-origin: 50% 55%;
  transform: perspective(90px) rotateX(30deg);
  animation: spinner-wiggle 5.2s infinite;
}

.spinner::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  margin: auto;
  width: 27px;
  height: 40px;
  background: linear-gradient(100deg, #24A4EA, #B76BF0);
  clip-path: polygon(0 0, 100% 50%, 0 100%);
  transform: translateX(4px);
  z-index: 0;
}

@keyframes spinner-wiggle {
  30% {
    transform: perspective(90px) rotateX(10deg);
  }

  40% {
    transform: perspective(90px) rotateX(7deg);
  }

  50% {
    transform: perspective(90px) rotateX(10deg);
  }

  60% {
    transform: perspective(90px) rotateX(8deg);
  }
}

.color-circle {
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  margin: auto;
  width: 90px;
  height: 90px;
  transform-origin: 50% 50%;
  background: linear-gradient(100deg, #24A4EA, #379DEB 25%, #B76BF0);
  border-radius: 50%;
  z-index: 0;
  box-shadow: inset 0 24px 18px -10px rgba(0, 0, 140, 0.3),
    inset 0 0 22px -2px rgba(0, 0, 0, 0.4);
  cursor: pointer;
  -webkit-mask-image: radial-gradient(circle, transparent 0 36px, black 36px);
  mask-image: radial-gradient(circle, transparent 0 50px, black 20px);
}

.spinner:hover .color-circle {
  background: -webkit-gradient(linear,
      left top,
      left bottom,
      color-stop(50%, rgba(34, 204, 0, 0.9)),
      color-stop(100%, #55ff00));
  animation: spin 1.7s infinite linear;
}

.color-circle:before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  margin: auto;
  width: 72px;
  height: 72px;
  border-radius: 50%;
  background-color: #353198;
  z-index: 0;
}

@-webkit-keyframes spin {
  0% {
    transform: rotateZ(0deg);
  }

  100% {
    transform: rotateZ(360deg);
  }
}

HTML

<div class=" spinner">
    <span class="color-circle"></span>
</div>

内容的提问来源于stack exchange，提问作者user17631451