html, body { 
    margin: 0; padding: 0; font-family: Arial, Helvetica, sans-serif; 
    line-height: 1.6; 
    color: #222; 
    background: #f5f5d5;}
main { max-width: 900px; 
    margin: 0 auto; 
    padding: 20px; 
}
nav { background: #222; 
    padding: 10px; 
    display: flex; 
    justify-content: center; 
    align-items: center; }
nav a { color: #fff; 
    text-decoration: none; 
    margin-right: 14px; 
    font-weight: bold; }
nav a:hover { text-decoration: underline; }
h1 { margin: 18px 0 6px; text-align: center; }
img { max-width: 100%; height: auto; display: block; margin: 10px auto; }
hr { border: 0; border-top: 1px solid #e5e5e5; margin: 18px 0; }
ul { padding-left: 20px; }