55.纯 CSS 创作一个太阳、地球、月亮的运转模型

<div class="container">
    <div class="sun"></div>
    <div class="earth">
        <div class="moon"></div>
    </div>
</div>

html, body {
    margin: 0;
    padding: 0;
}
/* 设置body子元素水平垂直居中 */
body{
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: black;
    /* 隐藏突出的部分 */
    overflow: hidden;
}
/* 设置.container容器尺寸 */
.container{
    position: relative;
    font-size: 10px;
    width: 40em;
    height: 40em;
    /* border: 1px solid white; */
}
/* 画出太阳 */
.sun{
    position: absolute;
    top: 15em;
    left: 15em;
    width: 10em;
    height: 10em;
    border-radius: 50%;
    box-shadow: 0 0 3em white;
    background-color: yellow;
}
/* 画出地球和月球的轨迹 */
.earth,
.earth .moon{
    position: absolute;
    border-width: 0.1em 0.1em 0 0;
    border-style: solid;
    border-color: white transparent transparent transparent;
    border-radius: 50%;
}
.earth{
    top: 5em;
    left: 5em;
    width: 30em;
    height: 30em;
    /* border: 1px solid white; */
    /* 设置动画  orbit: 轨道*/
    animation: orbit 36.5s linear infinite;
}
.earth .moon{
    top: 0;
    right: 0;
    width: 8em;
    height: 8em;
    /* border: 1px solid white; */
    animation: orbit 2.7s linear infinite;
}
@keyframes orbit {
    to {
        transform: rotate(360deg);
    }
}
/* 用伪元素画出地球和月球 */
.earth::before,
.earth .moon::before{
    position: absolute;
    content: ‘‘;
    border-radius: 50%;
}
.earth::before{
    top: 2.8em;
    right: 2.5em;
    width: 3em;
    height: 3em;
    background-color: aqua;
}
.earth .moon::before{
    top: 0.8em;
    right: 0.2em;
    width: 1.2em;
    height: 1.2em;
    background-color: silver;
}