body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #eef2f3;
    margin: 0;
    font-family: Arial, sans-serif;
}

.calculator {
    background: #ffffff;
    padding: 20px;
    border-radius: 12px;
    box-shadow: 0 8px 16px rgba(0,0,0,0.2);
}

#display {
    width: 100%;
    height: 50px;
    margin-bottom: 10px;
    font-size: 24px;
    text-align: right;
    padding: 10px;
    border-radius: 8px;
    border: 1px solid #ccc;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 60px);
    grid-gap: 10px;
    justify-content: center;
}

button {
    height: 60px;
    font-size: 20px;
    border: none;
    border-radius: 8px;
    background-color: #f0f0f0;
    cursor: pointer;
    transition: background-color 0.2s;
}

button:hover {
    background-color: #dcdcdc;
}

button.equal {
    grid-column: span 2;
    background-color: #4CAF50;
    color: white;
}

button.equal:hover {
    background-color: #45a049;
}