body {
    margin: 0;
    font-family: Arial, Helvetica, sans-serif;
    background-color: #f5f5f5;
    color: #333;
    line-height: 1.6;
}
header {
    text-align: center;
    padding: 20px 0;
}
header img {
    max-width: 200px;
    height: auto;
}
main {
    max-width: 900px;
    margin: 20px auto;
    padding: 30px;
    background: #fff;
    border: 1px solid #ccc;
    border-radius: 6px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}
h1, h2, h3 {
    color: #222;
    margin-top: 1.5em;
}
h1 {
    font-size: 1.8em;
    margin-top: 0;
}
h2 {
    font-size: 1.4em;
}
h3 {
    font-size: 1.2em;
}
a {
    color: #0066cc;
    text-decoration: none;
}
a:hover {
    text-decoration: underline;
}
ul {
    padding-left: 20px;
}
@media (max-width: 600px) {
    main {
    margin: 10px;
    padding: 20px;
    }
}