.container{
    margin: auto;
}

h1{
    font-size: 50px;
    font-family: Arial, Helvetica, sans-serif;
}

.calc{
    height: 370px;
    background: #3d4543;
    padding: 10px;
    border-radius: 20px;
    display: inline-block;
}
#answer {
    background: #08b84bdc;
    width: 370px;
    height: 80px;
    color: #000;
    border-radius: 10px;
    padding-right: 10px;
    margin-bottom: 10px;
    text-align: right;
    letter-spacing: 1px;
}
input{
    font-size: 30px;
    width: 65px;
    height: 55px;
    color: #fff;
    background:#6f6f6f;
    border-radius: 10px;
    margin: 5px;
    outline: none;
    border: 0px solid;
}

input[type="button"]:hover{
    cursor: pointer;
    background: #fff;
    color: #000;
}
.btn-red{
    background-color: red;
}

.btn-blue{
    background-color: skyblue;
}