body {
    background-color: #222;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    font-family: Arial, sans-serif;
}

.calculator {
    background-color: #333;
    padding: 20px;
    border-radius: 15px;
    box-shadow: 0 5px 15px rgba(0,0,0,0.3);
}

#display {
    width: 100%;
    height: 60px;
    font-size: 24px;
    text-align: right;
    margin-bottom: 10px;
    padding: 10px;
    border-radius: 8px;
    border: none;
    outline: none;
}

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

button {
    height: 60px;
    font-size: 20px;
    border: none;
    border-radius: 8px;
    background-color: #555;
    color: #fff;
    cursor: pointer;
    transition: 0.2s;
}

button:hover {
    background-color: #777;
}