body {
    font-family: Arial, sans-serif;
    background-color: #f4f4f4;
    margin: 0;
    padding: 20px;
    text-align: center;
}

nav {
    background-color: #333;
    padding: 10px 0;
}

nav a {
    color: white;
    margin: 0 15px;
    text-decoration: none;
}

nav a:hover {
    text-decoration: underline;
}

.calculator {
    background-color: white;
    display: inline-block;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 0 10px #ccc;
    margin-top: 20px;
}

#display {
    width: 100%;
    height: 40px;
    font-size: 20px;
    margin-bottom: 10px;
    text-align: right;
}

.buttons button {
    width: 50px;
    height: 50px;
    font-size: 18px;
    margin: 5px;
    cursor: pointer;
}

form {
    display: inline-block;
    text-align: left;
    margin-top: 20px;
    background: #fff;
    padding: 20px;
    border-radius: 10px;
}

input, textarea {
    width: 100%;
    padding: 8px;
    margin-top: 5px;
}