27.纯 CSS 创作一个精彩的彩虹 loading 特效

原文地址：https://segmentfault.com/a/1190000014939781

感想：正方形-》圆-》旋转一定角度-》动画-》隐藏下一半

HTML代码：

<div class="rainbow">
    <div class="bows">
        <span></span>
        <span></span>
        <span></span>
        <span></span>
        <span></span>
        <span></span>
    </div>
</div>

CSS代码：

html, body, .bows {
    margin: 0;
    padding: 0;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    background: white;
}
.rainbow {
    width: 20em;
    height: 10em;
    overflow: hidden;
}
.bows {
    position: relative;
    width: 100%;
    height: 200%;
    /* border: 1px solid blue; */
    transform: rotate(225deg);
}
.bows span {
    position: absolute;
    width: calc(100% - 2em * (var(--n) - 1));
    height: calc(100% - 2em * (var(--n) - 1));
    padding: 0;
    border: 1em solid var(--color);
    box-sizing: border-box;
    border-top-color: transparent;
    border-left-color: transparent;
    border-radius: 50%;
    animation: rotating 3s infinite;
    animation-delay: calc(0.05s * var(--n));
}
@keyframes rotating {
    0%, 20% {
        transform: rotate(0deg);
    }
    80%, 100% {
        transform: rotate(360deg);
    }
}
.bows span:nth-child(1) {
    --n: 1;
    --color: orangered;
}
.bows span:nth-child(2) {
    --n: 2;
    --color: orange;
}
.bows span:nth-child(3) {
  --n: 3;
  --color: yellow;
}
.bows span:nth-child(4) {
  --n: 4;
  --color: mediumspringgreen;
}
.bows span:nth-child(5) {
  --n: 5;
  --color: deepskyblue;
}
.bows span:nth-child(6) {
  --n: 6;
  --color: mediumpurple;
}