body {
    font-family: Arial, sans-serif;
    background-color: #f8fafc;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
}

.calculator {
    background: white;
    padding: 2rem;
    border-radius: 10px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

#display {
    width: 100%;
    font-size: 2rem;
    margin-bottom: 1rem;
}

.buttons button {
    padding: 1rem 1.5rem;
    margin: 0.25rem;
    font-size: 1.5rem;
}