body {
    background: #333333 url('bg_page.jpg') no-repeat fixed center center;
    background-size: cover;
    font-family: "Segoe UI", "Roboto", "Helvetica Neue", "Arial", "sans-serif";
    min-height: 900px;
}

#calender {
    background: url('bg_image.gif') no-repeat;
    width: 1200px;
    height: 859px;
    margin: 20px auto;
    padding-left: 45px;
    padding-top: 30px;
}

#calender .day {
    width: 80px;
    margin: 50px;
    height: 80px;
    display: block;
    float: left;
    text-align: center;
    vertical-align:middle;
    line-height: 80px;       /* the same as your div height */
    border: 2px dotted #ffffff;
    color: #000000;
    text-shadow: 1px 1px 2px #888;
}

#calender .day:hover {
    background-color:rgba(255, 255, 255, 0.5);
    color: #000000;
    cursor: pointer;
}

#overlay {
    width: 462px;
    height: 715px;
    padding: 5px;
    border-radius: 5px;
    z-index: 10;
    position: fixed;
    top: 50%;
    left: 50%;
    margin-top: -400px;
    margin-left: -300px;
    background: #EEEEEE;
}

#overlay .top {
    width: 100%;
    padding: 10px 0;
    background: #AAAAAA;
    text-align: center;
}

#overlay .top .right {
    float: right;
    text-align: right;
    cursor: pointer;
    font-weight: bold;
    padding-right: 15px;
}

.hidden {
    display: none;
}

@media only screen and (max-device-width:1024px) {
    form {
        width: 90%;
        margin: 0 auto;
    }

    input {
        width: 90%;
        font-size: 14pt;
        padding: 10px;
    }

    #overlay {
        height: 77%;
        width: 90%;
        position: fixed;
        top: 0;
        left: 0;
        margin: 10px;
    }

    .day {
        background-color:rgba(255, 255, 255, 0.25);
    }
}