body{
  text-align: center;

}
.calculator{
  border: 1px solid;
  display: inline-block;
  padding: 20px;
  border-radius: 20px;
  margin-top: 150px;
  border-radius: 20px;
}
input{
   margin-bottom: 20px;
   height: 40px;
   width: 250px;
}
button{
  height: 50px;
  width: 50px;
  margin: 10px;
  border-radius: 50px;
}
button:hover{
  background: lightcyan;
  color: red;
}