main.css

body{
    background-color: rgb(230, 225, 225);
}

#container{
    background-image: url("https://images.unsplash.com/photo-1518665750801-883c188a660d?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=967&q=80");
    background-repeat: no-repeat;
    height: 600px;
    width: 1000px;
    margin: 100px auto;
}

#calculator{
    background-color: black;
    width: 280px;
    height: 500px;
    margin: 0 auto;
    position: relative;
    top: 50px;
    border-radius: 30px;
}
 
#result{
    height: 130px;
}
#keyboard{
    height: 250px;
}

#history{
    text-align: right;
    color: white;
    margin: 0 20px;
    padding-top: 20px;
    font-size: 15px;
}
#output{
    text-align: right;
    color: white;
    margin: 0 20px;
    padding-top: 20px;
    font-size: 40px;
}

#output-value{
    margin: 0;
}

#keyboard{
    height: 400px;
}

button{
    height: 50px;
    width: 50px;
    margin: 10px;
    border-radius: 50%;
    border-width: 0;
    font-weight: bold;
    font-size: 15px;
    cursor: pointer;
    float: left;
}

button:focus{
    outline: 0;
}
    
button:active{
    font-size: 13px;
}

button:nth-of-type(4n){
    background-color: rgb(255, 151, 15);
}

button:nth-of-type(-n + 3){
    background-color: rgb(150, 148, 148);
}
button:last-child{
    background-color: rgb(255, 151, 15);
}

.numberZero{
    width: 120px;
    border-radius: 30px;
}

.number,.point{
    color: white;
    background-color: rgb(65, 65, 65);
}