body {
  font-family: Arial, sans-serif;
  background: #f9f9f9;
  margin: 0;
  padding: 0;
  color: #333;
}

header {
  background: #4a90e2;
  color: white;
  padding: 2rem;
  text-align: center;
}

header h1 {
  margin: 0;
  font-size: 2rem;
}

.container {
  max-width: 1100px;
  margin: 2rem auto;
  padding: 0 1rem;
}

h2 {
  color: #4a90e2;
  margin-top: 2rem;
  border-bottom: 2px solid #ddd;
  padding-bottom: 0.5rem;
}

.controls {
  margin-bottom: 1.5rem;
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
}

select, input[type="text"] {
  padding: 0.5rem;
  font-size: 1rem;
}

.course-list {
  list-style: none;
  padding: 0;
}

.course-list li {
  background: white;
  margin: 0.5rem 0;
  padding: 1rem;
  border-radius: 8px;
  box-shadow: 0 2px 5px rgba(0,0,0,0.05);
}

.course-list a {
  color: #4a90e2;
  text-decoration: none;
  font-weight: bold;
}

.course-list a:hover {
  text-decoration: underline;
}

.level, .language, .source {
  font-size: 0.9rem;
  color: #666;
  margin-left: 0.5rem;
}

.ad-banner {
  background: #f1f1f1;
  border: 1px dashed #ccc;
  text-align: center;
  padding: 1rem;
  margin: 1.5rem 0;
  border-radius: 8px;
}

footer {
  background: #333;
  color: white;
  text-align: center;
  padding: 1rem;
  margin-top: 3rem;
}

@media (max-width:768px) {
  .controls {
    flex-direction: column;
  }
}