body {
    margin: 0;
    font-family: Arial, sans-serif;
    background-color: #f3f4f6;
    color: #333;
}
header {
    background-color: #1f2937;
    color: white;
    padding: 1em;
    text-align: center;
}
nav {
    background-color: #374151;
    padding: 0.5em;
    text-align: center;
}
nav a {
    color: white;
    margin: 0 1em;
    text-decoration: none;
}
.container {
    max-width: 900px;
    margin: auto;
    padding: 1em;
}
.card {
    background-color: white;
    border: 1px solid #ddd;
    margin-bottom: 1em;
    padding: 1em;
    border-radius: 8px;
}
.card h3 {
    margin-top: 0;
}
footer {
    background-color: #1f2937;
    color: white;
    text-align: center;
    padding: 1em;
    margin-top: 2em;
}