是这么写的：
<div class="mdui-card">
            <div class="mdui-card-header">
                <img class="mdui-card-header-avatar" src="./res/head.jpg" />
                <div class="mdui-card-header-title">EASL启动器</div>
                <div class="mdui-card-header-subtitle">EASL YYDS</div>
            </div>
            <div class="mdui-card-primary" style="text-align: center;">
                <div class="mdui-card-primary-title">啓動游戲</div>
            </div>
            <div class="mdui-card-content">
                    <input type="text" id="username" placeholder="请输入ID" />
                    <br><br>
                    <input type="text" id="gameversion" placeholder="请输入要启动的游戏版本" />
                    <br><br>
                    <input id="microsoftLogin" type="checkbox" />
                    <label for="microsoftLogin">正版登录</label>
            </div>
            <div class="mdui-card-actions">
                <button class="mdui-btn mdui-ripple" onclick="start();">action 1</button>
                <button class="mdui-btn mdui-ripple" onclick="$('#noticeBox').toggle();">action 2</button>
                <button class="mdui-btn mdui-ripple" onclick="listVersion();">action 3</button>
            </div>
        </div>
卡片无法正常显示
