#main_container {
    width: 400px;
    margin: 20px;
    margin-left: auto;
    margin-right: auto;
    padding: 30px;
    font-family: sans-serif;
    border-radius: 20px;
    border: 3px solid #999;
}

#birth_date_input, #age_container {
    text-align: center;
    margin: 20px;
    margin-left: auto;
    margin-right: auto;
}

#age_container {
    margin: 40px 5px;
    padding: 20px;
    border-radius: 50px;
    border: 1px solid #000;
    font-weight: bolder;
    background: #EEE;
    font-size: 20px;
    line-height: 40px;
}

#calculate {
    cursor: pointer;
    text-align: center;
    width: 200px;
    padding: 5px;
    margin: 10px;
    margin-left: auto;
    margin-right: auto;
    border: 1px solid #999;
    border-radius: 10px;
    background: #FFD119;
    background: -webkit-gradient(linear, left top, left bottom, from(#FFD119), to(#E6B800));
	background: -moz-linear-gradient(top, #FFD119, #E6B800);
    font-weight: bold;
    height: 28px;
    box-shadow: 0 -8px inset;
}

#calculate:hover {
    background: -webkit-gradient(linear, left top, left bottom, from(#E6B800), to(#FFD119));
	background: -moz-linear-gradient(top, #E6B800, #FFD119);
    margin-top: 13px;
    height: 25px;
    box-shadow: 0 -5px inset;
}

#calculate:active {
    background: #403300;
    padding-top: 10px;
    height: 20px;
    box-shadow: 0 5px #000 inset;
}

#age {
    padding: 5px;
    border: 3px dashed #AAA;
    background-color: green;
}
html{
    background:rgb(100, 100, 1000);
}