效果预览按下右侧的“点击预览”按钮可以在当前页面预览，点击链接可以全屏预览。https://codepen.io/comehope/pen/odpRKX可交互视频教程此视频是可以交互的，你可以随时暂停视频，编辑视频中的代码。请用 chrome, safari, edge 打开观看。https://scrimba.com/c/cmQV7Hd源代码下载请从 github 下载。https://github.com/comehope/front-end-daily-challenges/tree/master/016-colorful-gradient-animated-border代码解读定义 dom，一个容器中包含一些文字：<div class="box"> you are my<br> FAVORITE</div>居中显示：html,body,.box { height: 100%; display: flex; align-items: center; justify-content: center;}设置页面背景色：body { background: #222;}设置容器和文字样式：.box { color: white; font-size: 2.5em; width: 10em; height: 5em; background: #111; font-family: sans-serif; line-height: 1.5em; text-align: center; border-radius: 0.2em;}用伪元素增加一个背板：.box { position: relative;}.box::after { content: ''; position: absolute; width: 102%; height: 104%; background-color: orange; z-index: -1; border-radius: 0.2em;}把背板设置为渐变色的：.box::after { /*background-color: orange;*/ background-image: linear-gradient(60deg, aquamarine, cornflowerblue, goldenrod, hotpink, salmon, lightgreen, sandybrown, violet);}为背板设置动画效果：.box::after { background-size: 300%, 300%; animation: animate_bg 5s ease infinite alternate;}@keyframes animate_bg { 0% { background-position: 0%, 50%; } 50% { background-position: 100%, 50%; } 100% { background-position: 0%, 50%; }}最后，再为文字增加变色效果：.box { animation: animate_text 2s linear infinite alternate;}@keyframes animate_text { from { color: lime; } to { color: yellow; }}大功告成！知识点z-index https://developer.mozilla.org/en-US/docs/Web/CSS/z-indexbackground-image https://developer.mozilla.org/en-US/docs/Web/CSS/background-imagebackground-size https://developer.mozilla.org/en-US/docs/Web/CSS/background-sizebackground-position https://developer.mozilla.org/en-US/docs/Web/CSS/background-position
