body {
  font-family: courier;
}
#container {
  text-align: center;
  padding: 20px;
}
#form{
  margin-top: 20px;
}
input[type='text'] {
  padding: 5px 10px;
  border: 1px solid #bdc3c7;
  outline: 0;
  color: #2980b9;
  font-weight: bold;
}
#calbtn {
  border: 0;
  padding: 10px 20px;
  cursor: pointer;
  background: #d35400;
  color: #f1c40f;
  font-size: 20px;
  outline: 0;
}
#calbtn:hover, #calbtn:active {
  background-color: #c0392b;
  outline: 0;
}
span {
  display: inline-block;
  font-size: 45px;
  font-weight: bold;
  color: #27ae60;
}