div[class^="content-"] {
  text-align: center;
  padding: 20px 15px;
  margin: 10px auto;
  max-width: 900px;
}

.content-3 h1 {
  font-size: 2.2rem;
  font-weight: 800;
  color: #0d6efd;
  text-transform: uppercase;
  margin-bottom: 10px;
  text-shadow: 1px 1px 3px rgba(0, 0, 0, 0.1);
}

.content-4 h2,
.content-5 h2,
.content-6 h2 {
  font-size: 1.5rem;
  font-weight: 700;
  color: #212529;
  background-color: #e9f5ff;
  border-left: 5px solid #0d6efd;
  padding: 12px 20px;
  border-radius: 8px;
  display: inline-block;
  margin: 10px 0;
}

.content-7 p {
  font-size: 1.3rem;
  font-weight: bold;
  color: #dc3545;
  background-color: #fff3f3;
  padding: 10px 20px;
  border-radius: 6px;
  display: inline-block;
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.1);
}

.content-7 a {
  color: #0053ce;
  text-decoration: none;
  font-weight: bold;
}

.content-8 {
  background-color: #ffffff;
  padding: 30px 20px;
  max-width: 900px;
  margin: 30px auto;
  border-radius: 12px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
  line-height: 1.8;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  color: #333;
}

.viet-1 {
  font-size: 1.1rem;
  margin-bottom: 20px;
}

.viet-2 {
  font-size: 1.1rem;
  margin-bottom: 20px;
  background-color: #f0f8ff;
  border-left: 5px solid #0d6efd;
  padding: 15px;
  border-radius: 6px;
}

.viet-3 {
  font-size: 1.15rem;
  font-weight: bold;
  color: #0c5460;
  margin-bottom: 25px;
}

.viet-a1 {
  display: inline-block;
  background-color: #dc3545;
  color: #fff;
  text-decoration: none;
  padding: 12px 24px;
  font-size: 1.1rem;
  border-radius: 6px;
  font-weight: bold;
  transition: background-color 0.3s ease, transform 0.2s ease;
}

.viet-a1:hover {
  background-color: #c82333;
  transform: scale(1.05);
}

.content-video1 {
  width: 100%;
  max-width: 100%;
  aspect-ratio: 16 / 9;
  margin: 20px auto;
  border-radius: 12px;
  overflow: hidden;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.content-video1 iframe {
  width: 100%;
  height: 100%;
  border: none;
  border-radius: 12px;
  display: block;
}

.content-9 {
  background-color: #f8f9fa;
  border-left: 5px solid #0d6efd;
  padding: 25px 30px;
  margin: 30px auto;
  border-radius: 10px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.05);
  max-width: 800px;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}