前端每日实战：2.纯 CSS 创作一个矩形旋转 loader 特效

<div class="loader">
      <span></span>
      <span></span>
      <span></span>
 </div>

/* 居中显示 */
html, body {
    margin: 0;
    padding: 0;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: black;
}
/* 设置容器的尺寸： */
.loader {
    width: 150px;
    height: 150px;
    position: relative;
}
/* 设置矩形的边框样式 */
.loader span {
    position: absolute;
    box-sizing: border-box;
    
    border-radius: 50%;
    
}
/* 设置 3 个矩形的尺寸： */
.loader span:nth-child(1) {
    border: 5px solid red;
    width: 100%;
    height: 100%;
}
.loader span:nth-child(2) {
    border: 5px solid green;
    width: 70%;
    height: 70%;
    margin: 15%;
}
.loader span:nth-child(3) {
    border: 5px solid blue;
    width: 40%;
    height: 40%;
    margin: 30%;
}
/* 定义动画效果：*/
@keyframes rotating1 {
    from {
        transform: rotateY(0deg);
    }

    to {
        transform: rotateY(360deg);
    }
}
/* 把动画应用到 3 个矩形上：*/
.loader span:nth-child(1) {
    animation: rotating1 linear infinite;
    animation-duration: 4s;
}
/* 定义动画效果：*/
@keyframes rotating2 {
    from {
        transform: rotateX(0deg);
        transform-origin:center center;
    }

    to {
        transform: rotateX(360deg);
    }
}
/* 把动画应用到 3 个矩形上：*/
.loader span:nth-child(2) {
    animation: rotating2 linear infinite;
    animation-duration: 4s;
}
/* 定义动画效果：这里无效  需补充*/
@keyframes rotating3 {
    from {
        skew(0deg,0deg);
    }
    to {
        skew(360deg,360deg);
    }
}
/* 把动画应用到 3 个矩形上：*/
.loader span:nth-child(3) {
    animation: rotating3 linear infinite;
    animation-duration: 4s;
}