CSS组件之文本输入框(input text)样式

<!DOCTYPE HTML>
<html>
<head>
    <meta charset="utf-8">
    <title>三十课 - CSS组件之文本输入框(input text)样式</title>
    <style>
        .ke30-label {
            position: relative;
            margin-bottom: 20px;
        }
        .ke30-label label {
            position: absolute;
            top: 14px;
            left: 7px;
            padding: 0 5px;
            -webkit-transition: top .5s, font-size .3s;
            transition: top .5s, font-size .3s;
        }
        .ke30-label input {
            height: 45px;
            padding: 0 12px;
        }
        .ke30-label input:hover + label, .ke30-label input:focus + label, .ke30-label input:valid + label {
            top: -9px;
            font-size: 12px;
        }
        label {
            color: #000;
            background: #fff;
        }
        input {
            color: #000;
            border: 2px solid #289afa;
            background: #fff;
            width: 240px;
            outline: 0;
        }
        body > div {
            padding: 1rem 0 0 1rem;
        }
    </style>
</head>
<body>
<div>
    <div class="ke30-label">
        <input type="text" id="username" required>
        <label for="username">用户名</label>
    </div>
    <div class="ke30-label">
        <input type="text" id="password" required>
        <label for="password">密码</label>
    </div>
</div>
</body>
</html>