body {
  font-family: 'Segoe UI', Arial, sans-serif;
  background: #e6f0fa;
  color: #123a5d;
  margin: 0;
  padding: 0;
}
header {
  background: #1565c0;
  color: #fff;
  padding: 1.5rem 0;
  text-align: center;
}
.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: center;
  margin: 1rem 0;
}
.controls input, .controls select, .controls button {
  padding: 0.5rem;
  border-radius: 4px;
  border: 1px solid #90caf9;
  font-size: 1rem;
}
.courses-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 1.5rem;
  margin: 2rem;
}
.course-card {
  background: #fff;
  border-radius: 8px;
  box-shadow: 0 2px 8px #90caf9;
  padding: 1.5rem;
  transition: box-shadow 0.2s;
  cursor: pointer;
}
.course-card:hover {
  box-shadow: 0 4px 16px #1976d2;
}
.modal {
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  background: rgba(21, 101, 192, 0.2);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
}
.modal-content {
  background: #fff;
  border-radius: 8px;
  padding: 2rem;
  min-width: 320px;
  max-width: 90vw;
  box-shadow: 0 2px 16px #1976d2;
  position: relative;
}
.close-btn {
  position: absolute;
  top: 1rem;
  right: 1rem;
  font-size: 2rem;
  color: #1976d2;
  cursor: pointer;
}
@media (max-width: 600px) {
  .courses-grid {
    grid-template-columns: 1fr;
    margin: 1rem;
  }
  .modal-content {
    min-width: 90vw;
    padding: 1rem;
  }
}