#main_container
{
    width: 450px;

 margin: 20px;

  margin-left: auto;

  margin-right: auto;

 padding: 30px;

 font-family: sans-serif;

 border-radius: 5px;

 border: 3px solid #999;

 background: #00bfff;

}

#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: 5px;

border: 1px solid #999;

font-weight: bolder;

   background: #EEE;

   font-size: 20px;

  line-height: 40px;
}
.hedding {

  color: #fff;

 text-transform: uppercase;

 font-size: 27px;

font-weight: bold;

  margin-bottom: 20px;

}

#age span{
    color:green;

}

#calculate {
    border-radius: 2px;

   background-color: #0db9f2;

  border: 1px solid #fff;

 color: #FFFFFF;

 text-align: center;

  font-size: 20px;

padding: 8px 27px;

width: 200px;

transition: all 0.5s;

   cursor: pointer;

  margin: 0 auto;
}

#calculate span {
    cursor: pointer;
    display: inline-block;
    position: relative;

  transition: 0.5s;
}

#calculate span:after {
    content: ">";

   position: absolute;

  opacity: 0;

 top: 0;

 right: -20px;

  transition: 0.5s;
}
#calculate:hover span {
    padding-right: 25px;
}
#calculate:hover span:after {
    opacity: 1;
    right: 0;
}
#birth_date_input input[type="date" i]
{
    padding: 5px;

   width: 58%;
}