body{
    background: -webkit-gradient(linear, left bottom, left top, 
    from(rgba(7, 203, 238, 1.9)), to(rgba(0, 0, 0, 2.2)));
    font-family: cursive;
    color: aqua;
    text-align: center;
    font-size: 1.2rem;
}

#container{
    width: 900px;
    height: 500px;
    background-image: linear-gradient(rgba(0,0,0,0.3), rgba(0,0,0,0.3)),url(bcg.jpg);
    margin: 10px auto;
}

#calculator{
    width: 290px;
    height: 470px;
    background-color:#25CCF7;
    margin: 0 auto;
    border-radius: 20px;
    border: 4px solid black;
    top: 10px;
    position: relative;
    box-shadow: 0 5px 8px 2px ;
}

#result{
    height: 120px;
}

#history{
    text-align: right;
    height: 20px;
    margin: 0 20px;
    padding-top: 20px;
    font-size: 15px;
    color: #616C6F;
}

#output{
    text-align: right;
    height: 60px;
    margin: 10px 20px;
    font-size: 35px;
    color: black;
}

#keyboard{
    height: 400px;

}

.operator , .empty , .number{
    height: 50px;
    width: 50px;
   float: left;
   margin: 10.5px;
   border-radius: 50%;
   border-width: 0;
   font-weight: bold;
   font-size: 15px;
  
}

.operator{
    background-color: #616C6F;
}

.number , .operator{
    cursor: pointer;
}

/* .number , .operator button:hover{
    transform: scale(1.05);
} */

.number , .empty{
    background-color: #25CCF7;
}

.operator:active , .number:active{
    font-size: 25px;
}

.empty:focus , .number:focus , .operator:focus{
    outline: 0;
}

button:nth-child(4){
    background-color: #EA7773;
}

button:nth-child(8){
    background-color: #1287A5;
}

button:nth-child(12){
    background-color: #EEC213;
}

button:nth-child(16){
    background-color: #FF3031;
}

button:nth-child(20){
    background-color: #A3CB37;
}