/* Element selector */
body {
  background: #f4f6fb;
  font-family: "Verdana", sans-serif;
  color: #222;
  margin: 0;
  line-height: 1.6;
}

/* ID selector */
#page-header {
  background-color: #2a4b8d;
  color: white;
  text-align: center;
  padding: 20px 0;
}

#page-header nav a {
  color: #ffcc00;
  text-decoration: none;
  margin: 0 10px;
}
#page-header nav a:hover {
  text-decoration: underline;
}

/* Class selector */
.topic-heading {
  color: #b22222;
  border-bottom: 2px solid #b22222;
  display: inline-block;
  padding-bottom: 5px;
}

article {
  background: white;
  margin: 25px auto;
  padding: 20px;
  border-radius: 8px;
  max-width: 700px;
  box-shadow: 0 2px 6px rgba(0,0,0,0.1);
}

img {
  display: block;
  margin: 15px auto;
  border: 1px solid #ccc;
  border-radius: 5px;
}

button {
  background-color: #2a4b8d;
  color: white;
  border: none;
  border-radius: 4px;
  padding: 10px 15px;
  cursor: pointer;
}
button:hover {
  background-color: #b22222;
}

footer {
  text-align: center;
  background-color: #2a4b8d;
  color: white;
  padding: 10px;
  margin-top: 20px;
}