body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background: anti-flash white;
    margin: 0;
}
.calculator {
    background: shorthand white;
    padding: 20px;
    border-radius: 15px;
    box-shadow: 0 8px 16px rgba(0, 0, 0, 0.2);
    width: 300px;
}
#display {
    width: 100%;
    height: 50px;
    font-size: 1.5rem;
    text-align: right;
    margin-bottom: 10px;
    padding: 5px 10px;
    border: 2px solid #ccc;
    border-radius: 8px;
}
.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}
button {
    padding: 15px;
    font-size: 1.2rem;
    border: none;
    border-radius: 8px;
    background-color: whitesmoke;
    cursor: pointer;
    transition: background-color 0.3s;
}
button:hover {
    background-color: gainsboro;
}
.zero {
    grid-column: span 2;
}