<style>
    html {
        background: #ECF0F1;
        margin: 0;
        padding: 0;
    }
    body {
        font-family: Arial, Helvetica, sans-serif;
        line-height: 1.5em;
        padding: 0.8em;
        max-width: 30em;
        margin: 1em auto;
        background: #fff;
        border: 4px solid #BDC3C7;
        box-shadow: 0 0 10px #ddd;
    }
    a {
        color: #2980B9;
        text-decoration: none;
        border-bottom: 1px dotted #2980B9;
    }
    a:hover, a:active {
        color: #3498DB;
        border-bottom: 1px solid #2980B9;
    }
    header {
        text-align: center;
        margin-bottom: 1em;
    }
    .des {
        display: block;
        font-size: 0.8em;
    }
    .img {
        width: 80;
        height: 20;
        color: #E74C3C;
        display: block;
        margin: 0.5em 0;
    }
    .logo {
        font-size: 5em;
        color: #E74C3C;
        display: block;
        margin: 0.5em 0;
    }
    h1 {
        margin: 0;
        color: #555;
        font-family: Georgia;
        font-weight: normal;
        font-size: 1.2em;
    }
    h2 {
        font-size: 0.8em;
        color: #aaa;
        font-weight: normal;
        margin: 0;
    }
    nav ul {
        list-style: none;
        margin: 0;
        padding: 0;
        overflow: hidden;
    }
    nav li {
        margin: 0 1px 1px 0;
        float: left;
        width: 49.6%;
    }
    nav li a {
        font-size: 0.9em;
        display: block;
        color: #fff;
        background: #E74C3C;
        text-align: center;
        border: 0 none;
        padding: 0.5em 0;
    }
    nav li a:hover, nav li a:active {
        border: 0 none;
        background: #C0392B;
        color: #fff;
    }
    .content {
        margin: 1em 0;
    }
    article {
        margin: 0.5em;
        height: 18em;
        background: #34495E;
    }
    footer {
        text-align: center;
        color: #34495E;
        font-size: 0.8em;
    }    
    
    /* Dialog */
    #overlay {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        background: #000;
        opacity: 0.9;
        display: none;
    }
    #dialog {
        position: absolute;
        top: 16%;
        left: 35%;
        width: 30%;
        border: 4px solid #ccc;
        background: #fff;
        display: none;
    }
    #dialog h2 {
        margin: 0;
        padding: 8px;
        background: #ddd;
        font-size: 17px;
    }
    #dialog h2 span {
        display: block;
        float: right;
        padding: 0 5px;
        color: #c22;
        cursor: pointer;
    }
    #dialog form {
        padding: 20px;
    }
    input[type=text] {
        padding: 6px;
        width: 90%;
    }
    textarea {
        padding: 6px;
        font-family: Arial, Helvetica, sans-serif;
        width: 90%;
        height: 140px;
    }
    input[type=submit] {
        padding: 8px 18px;
        margin-top: 10px;
    }
    #btn {
        position: absolute;
        top: 50%;
        left: 45%;
        width: 20%;
        border: 4px solid #ccc;
        text-align: center;
        background: #fff;
        opacity: 0.6;
        display: none;       
        }
    
    @media (min-width: 20em) {
        article {
            width: 100%;
        }
        #btn {
            top: 65%;
            left: 30%;
            width: 50%;
            }
    }

    @media (min-width: 33em) {
        body {
            padding: 1.6em;
            max-width: 60em;
        }
        header {
            overflow: hidden;
            text-align: left;
        }
            .logo {
            float: left;
        }
            hgroup {
            float: left;
            margin: 1.6em 0 0 1em;
        }
        .des {
            float: right;
            margin-top: 3em;
        }
        h1 {
            font-size: 1.6em;
        }
        nav {
            background: #E74C3C;
        }
        nav ul li {
            width: auto;
            border-right: 1px solid #C0392B;
        }
        nav ul li a {
            font-size: 1em;
            padding: 0.5em 3em;
        }
        .content {
            overflow: hidden;
        }
        article {
            width: 100%;
        }
        #btn {
            top: 50%;
            left:40%;
            width: 20%;
        }
    }
    @media (min-width: 30em) and (max-width: 60em) {
        body {
            width: 100%;
            height: auto;
        }
        .des {
            display: block;
            float: none;
            text-align: center;
            margin-top: 0;
        }
        nav {
            background: transparent;
        }
        nav ul li {
            width: 33%;
            border: 0 none;
        }
        article {
            width: 100%;
        }
        #btn {
            top: 40%;
            left:30%;
            width: 50%;
        }
    }

    @media (min-width: 30em) and (max-width: 40em) {
        #btn {
            top: 180%;
            left:30%;
            width: 50%;
        }
    }
</style>
