body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    line-height: 1.6;
    margin: 0;
    background-color: #f9f9f9;
    color: #333;
}
.container {
    max-width: 900px;
    margin: 2rem auto;
    padding: 1rem 2rem;
    background-color: #fff;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}
nav {
    background-color: #eee;
    padding: 1rem;
    border-radius: 5px;
    margin-bottom: 2rem;
    text-align: center;
}
nav a {
    text-decoration: none;
    color: #007bff;
    font-weight: 500;
    padding: 0.5rem 1rem;
    transition: background-color 0.2s;
}
nav a:hover {
    background-color: #ddd;
    border-radius: 5px;
}
h1, h2 {
    color: #111;
}
header {
    text-align: center;
    border-bottom: 1px solid #eee;
    padding-bottom: 1rem;
    margin-bottom: 2rem;
}
.nav-active {
    text-decoration: none;
    color: #333; 
    font-weight: 700; 
    padding: 0.5rem 1rem;
    background-color: #e0e0e0;
    border-radius: 5px;
    cursor: default; 
}