body {
    font-family: sans-serif;
    background-color: #fff;
    color: #000;
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
}

.container {
    text-align: center;
    max-width: 800px;
    padding: 20px;
}

nav {
    margin-bottom: 20px;
}

nav a {
    text-decoration: none;
    color: #000;
    margin: 0 15px;
    font-weight: bold;
}

nav a.active {
    text-decoration: underline;
}

#login-form {
    display: flex;
    flex-direction: column;
    align-items: center;
}

#login-form input {
    margin-bottom: 10px;
    padding: 8px;
    width: 200px;
}

.error {
    color: red;
    margin-top: 10px;
}

.calculator {
    margin-top: 30px;
}

.calculator input {
    padding: 8px;
    margin-right: 10px;
}

#results {
    margin-top: 20px;
    text-align: left;
}