如何用纯 CSS 创作炫酷的同心矩形旋转动画
效果预览
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https://codepen.io/comehope/pen/bMvbRp
可交互视频教程
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请用 chrome, safari, edge 打开观看。
https://scrimba.com/p/pEgDAM/cp2dZcQ
源代码下载
本地下载请从 github 下载。
代码解读
定义 dom,一个容器中包含一个 span:
<div class="loader">
<span></span>
</div>
居中显示:
html,
body,
.loader {
height: 100%;
display: flex;
align-items: center;
justify-content: center;
background-color: black;
}
设置 span 的样式:
.loader {
width: 10em;
height: 10em;
font-size: 28px;
position: relative;
}
.loader span {
position: absolute;
width: 100%;
height: 100%;
background-color: rgba(100%, 0%, 0%, 0.3);
box-sizing: border-box;
border: 0.5em solid;
border-color: white rgba(100%, 100%, 100%, 0.2);
}
在 dom 中把 span 增加到 5 个:
<div class="loader">
<span></span>
<span></span>
<span></span>
<span></span>
<span></span>
</div>
分别设置 5 个 span 的尺寸:
.loader span:nth-child(1) {
width: calc(20% + 20% * (5 - 1));
height: calc(20% + 20% * (5 - 1));
}
.loader span:nth-child(2) {
width: calc(20% + 20% * (5 - 2));
height: calc(20% + 20% * (5 - 2));
}
.loader span:nth-child(3) {
width: calc(20% + 20% * (5 - 3));
height: calc(20% + 20% * (5 - 3));
}
.loader span:nth-child(4) {
width: calc(20% + 20% * (5 - 4));
height: calc(20% + 20% * (5 - 4));
}
.loader span:nth-child(5) {
width: calc(20% + 20% * (5 - 5));
height: calc(20% + 20% * (5 - 5));
}
增加颜色变幻的动画效果:
.loader span {
animation: animate 5s ease-in-out infinite alternate;
}
@keyframes animate {
0% {
/* red */
background-color: rgba(100%, 0%, 0%, 0.3);
}
25% {
/* yellow */
background-color: rgba(100%, 100%, 0%, 0.3);
}
50% {
/* green */
background-color: rgba(0%, 100%, 0%, 0.3);
}
75% {
/* blue */
background-color: rgba(0%, 0%, 100%, 0.3);
}
100% {
/* purple */
background-color: rgba(100%, 0%, 100%, 0.3);
}
}
再增加旋转效果:
@keyframes animate {
0% {
transform: rotate(0deg);
}
100% {
transform: rotate(720deg);
}
}
最后,为每个 span 设置动画延时,增加动感:
.loader span:nth-child(1) {
animation-delay: calc(0.2s * (5 - 1));
}
.loader span:nth-child(2) {
animation-delay: calc(0.2s * (5 - 2));
}
.loader span:nth-child(3) {
animation-delay: calc(0.2s * (5 - 3));
}
.loader span:nth-child(4) {
animation-delay: calc(0.2s * (5 - 4));
}
.loader span:nth-child(5) {
animation-delay: calc(0.2s * (5 - 5));
}
知识点
- border-color https://developer.mozilla.org/en-US/docs/Web/CSS/border-color
- calc() https://developer.mozilla.org/en-US/docs/Web/CSS/calc
- rotate() https://developer.mozilla.org/en-US/docs/Web/CSS/transform-function/rotate
- animation-delay https://developer.mozilla.org/en-US/docs/Web/CSS/animation-delay