25.纯 CSS 创作一个慧星拖尾效果的 loader 动画

原文地址：https://segmentfault.com/a/1190000014916281

简化地址：https://codepen.io/pen/?editors=1100

HTML代码：

<div class="loader">
    <div class="face">
        <div class="circle"></div>
    </div>
    <div class="face">
        <div class="circle"></div>
    </div>
</div>

CSS代码：

html,
body,
.loader {
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: black;
}
.loader {
    width: 200px;
    height: 200px;
    position: relative;
}
.loader .face {
    position: absolute;
    border: 2px solid transparent;
    border-radius: 50%;
    border-top-color: var(--color);
    border-left-color: var(--color);
    animation: animate 3s linear infinite;
}
.loader .face:nth-child(1) {
    width: 100%;
    height: 100%;
    --color: gold;
    --deg: 0deg;
}
.loader .face:nth-child(2) {
    width: 70%;
    height: 70%;
    --color: lime;
    --deg: 180deg;
    animation-direction: reverse;
}
.loader .face .circle {
    position: absolute;
    width: 50%;
    height: 1px;
    top: 50%;
    left: 50%;
    background-color: transparent;
    transform: rotate(calc(var(--deg) - 45deg));
    transform-origin: left;
}
.loader .face .circle::before {
    position: absolute;
    top: -5px;
    right: -5px;
    content: '';
    width: 10px;
    height: 10px;
    background-color: var(--color);
    border-radius: 50%;
    box-shadow: 0 0 20px var(--color),
                0 0 40px var(--color),
                0 0 60px var(--color),
                0 0 80px var(--color),
                0 0 100px var(--color),
                0 0 0 5px rgba(255, 255, 0, 0.1);
}
@keyframes animate {
    from {
        transform: rotate(0deg);
    }
    to {
        transform: rotate(360deg);
    }
}