body {
    font-family: Arial, sans-serif;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    background-color: #f0f0f0;
    background-image: url("https://play-lh.googleusercontent.com/GhLZnqVu4XdqLH74yB9jfoMEIFdS2S3KN2rMKHsWapYYd0eCIjJAGXcY2x8TfedCqUo");
    background-position: center;
    background-size: auto;
}

.calculator {
    background-color: white;
    border-radius: 10px;
    padding: 20px;
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.1);
}

.display {
    width: 100%;
    height: 50px;
    font-size: 2rem;
    text-align: right;
    padding: 10px;
    margin-bottom: 20px;
    border: 1px solid #ccc;
    border-radius: 5px;
    box-sizing: border-box;
    user-select: none;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    user-select: none;
}

.button {
    padding: 20px;
    font-size: 1.5rem;
    border: 1px solid #ccc;
    border-radius: 5px;
    background-color: #f1f1f1;
    cursor: pointer;
    transition: background-color 0.3s;
}

.button:hover {
    background-color: #ddd;
}

.button:active {
    background-color: green;
}

footer {
    margin-top: 100px;
    user-select: none;

    a {
        color: white;
        text-decoration: none;
        user-select: none;
    }
}