body {
    font-family: Arial, sans-serif;
    background-color: #f4f4f4;
    margin: 0;
    padding: 0;
}

.container {
    max-width: 800px;
    margin: 50px auto;
    background-color: #fff;
    padding: 20px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

h1, h2 {
    text-align: center;
}

form label {
    margin-top: 10px;
    display: block;
}

form input {
    width: 100%;
    padding: 8px;
    margin: 5px 0;
    box-sizing: border-box;
}

button {
    background-color: #4CAF50;
    color: white;
    padding: 10px;
    border: none;
    cursor: pointer;
    font-size: 16px;
    margin-top: 20px;
}

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

.invoice-details {
    width: 100%;
    border-collapse: collapse;
    margin-top: 20px;
}

.invoice-details, th, td {
    border: 1px solid #ddd;
}

.invoice-details th, td {
    padding: 8px;
    text-align: left;
}

h3 {
    text-align: center;
    margin-top: 20px;
}