styles.css

@import url('https://fonts.googleapis.com/css?family=Montserrat');
body{
    padding: 75px;
    background-color: rgb(0, 0, 0);
}
.calculator {
    height: 540px;
    width: 350px;
    margin: 0 auto;
    padding: 10px;
    background-color: #000000;
    border: 1px solid #ccc;
    border-radius: 15px;
}
 
input[type="text"] {
    width: 97%;
    height: 100px;
    margin-bottom: 10px;
    font-size: 30px;
    border: 0px;
    background-color: #000000;
    color: #eee;
}

.horizontal-line {
    border-top: 1px solid #c2b9b9;
    padding-bottom: 10px;
}

.button-row {
    display: flex;
    font-family: "Montserrat", sans-serif;
    padding-bottom: 15px;
    justify-content: space-between;
}

.button {
    width: 70px;
    height: 70px;
    font-size: 20px;
    text-align: center;
    color: #eee;
    line-height: 70px;
    cursor: pointer;
    font-weight: bold;
    border-radius: 40px;
}

.button:hover {
    background-color: #eccbcb;
}

.zero{
    width: 160px;
}

.orange{
    color: orangered;
}

.equal{
    background-color: orangered;
}