<div class="container"></div>

body{
  background: #FFFFD4;
}

.container{
  width: 100px;
  height: 100px;
  background: #9DAF75;
  border: 5px solid #1F2C12;
  margin: 0 auto;
}
/*

*/

@media screen and (min-width:650px){
  body{
    background: #1F2C12;
  }
  .container{
    width:250px;
    height: 250px;
    background: #FFFFD4;
    border: 5px solid #9DAF75;
    margin: 0 auto;
    border-radius: 25%;
  }
}