styles.css

body {
    margin: 0;
    padding: 0;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

#calculator {
    background-color: black;
    height: 640px;
    width: 360px;
    border-radius: 20px;
    display: flex;
    flex-direction: column;
}

#display {
    margin: 10px;
    border: 1px dotted white;
    border-radius: 16px;
    height: 36%;
    color: white;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    text-align: right;
}

#upper {
    font-size: small;
    height: 20px;
}

#lower {
    font-size: 1.8rem;
    font-weight: bold;
    height: 36px;
}

p{
    margin: 0px 16px 16px 0px;
}

#buttons {
    display: flex;
    flex-direction: column;
    margin: 10px;
    flex-grow: 1;
}

.row {
    display: flex;
    flex-grow: 1;
    justify-content: space-evenly;
}

button {
    border-radius: 50%;
    /* flex-grow: 1; */
    height: 80px;
    width: 80px;
    margin: 2px;
    font-size: 1.7rem;
    font-weight: bold;
    color: white;
}

#zero {
    /* flex-grow: 2; */
    width: 160px;
    border-radius: 40px;
}

.yellow {
    background-color: orange;
}

.ash {
    background-color: #b2beb5;
}

.digit {
    background-color: gray;
}

#ac, #sign, #percent {
    color: black;
}