/* Base page styling */
body {
  background-color: #f5f8fb;   /* light background */
  color: #222;                  /* readable text */
  font-family: Arial, Helvetica, sans-serif;
  margin: 10px;
}

/* Center the main header, nav, and footer (required) */
h1, nav, footer {
  text-align: center;
}
h2, nav, footer {text-align: center;
}

/* Simple horizontal nav */
nav a {
  margin: 0 10px;
  text-decoration: none;
  font-weight: 600;
}
nav a:hover { text-decoration: underline; }

/* Content readability */
main { max-width: 900px; margin: 0 auto; }
p { line-height: 1.6; font-size: 1rem; }

/* Images and figure captions */
img { max-width: 100%; height: auto; display: block; margin: 10px auto; }
figure { margin: 20px auto; max-width: 900px; }
figcaption { text-align: center; font-style: italic; margin-top: 6px; }

<style>
iframe {
  border: none;
}
</style