css 动态边框 前端 537 一页书 2021-01-18 16:29:16 ```html body { display: flex; justify-content: center; align-items: center; height: 100vh; } *, *::before, *::after { box-sizing: border-box; } @keyframes rotate { 100% { transform: rotate(1turn); } } .rainbow { position: relative; z-index: 0; width: 400px; height: 300px; border-radius: 10px; overflow: hidden; padding: 2rem; &::before { content: ''; position: absolute; z-index: -2; left: -50%; top: -50%; width: 200%; height: 200%; background-color: #399953; background-repeat: no-repeat; background-size: 50% 50%, 50% 50%; background-position: 0 0, 100% 0, 100% 100%, 0 100%; background-image: linear-gradient(#399953, #399953), linear-gradient(#fbb300, #fbb300), linear-gradient(#d53e33, #d53e33), linear-gradient(#377af5, #377af5); animation: rotate 4s linear infinite; } &::after { content: ''; position: absolute; z-index: -1; left: 6px; top: 6px; width: calc(100% - 12px); height: calc(100% - 12px); background: white; border-radius: 5px; animation: opacityChange 3s infinite alternate; } } @keyframes opacityChange { 50% { opacity:1; } 100% { opacity: .5; } } ```