styles.css

body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
}

header {
    background-color: #333;
    padding: 10px;
    text-align: center;
    color: #fff;
    font-size: 24px;
    font-weight: bold;
    border-bottom: 3px solid #000;
}

.menu {
    display: flex;
    justify-content: space-around;
    background-color: #333;
    padding: 10px;
    border-bottom: 3px solid #000;
}

.menu a {
    text-decoration: none;
    color: #fff;
    font-size: 18px;
    padding: 10px;
    border-radius: 10px;
    background-color: #555;
    transition: background-color 0.3s;
}

.menu a:hover {
    background-color: #777;
}

.container {
    max-width: 800px;
    margin: 20px auto;
    padding: 20px;
    background-color: #f9f9f9;
    border: 1px solid #ddd;
    border-radius: 10px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}

h1 {
    font-size: 24px;
    margin-bottom: 20px;
}

form {
    margin-bottom: 20px;
}

label {
    display: block;
    margin-bottom: 5px;
}

input[type="number"],
select {
    width: 100%;
    padding: 10px;
    font-size: 16px;
    border-radius: 5px;
    border: 1px solid #ddd;
    margin-bottom: 10px;
}

input[type="submit"] {
    background-color: #555;
    color: #fff;
    border: none;
    padding: 10px 20px;
    font-size: 16px;
    border-radius: 5px;
    cursor: pointer;
}

.result {
    margin-top: 20px;
    font-size: 18px;
    background-color: #f0f0f0;
    padding: 10px;
    border-radius: 5px;
}