.course-shell {
  transition: grid-template-columns .22s ease, gap .22s ease;
}

.course-sidebar {
  overflow: visible;
  transition: opacity .16s ease;
}

.course-sidebar-content {
  max-height: calc(100vh - 130px);
  overflow: auto;
}

.sidebar-toggle {
  position: absolute;
  top: 0;
  right: -29px;
  z-index: 9;
  width: 29px;
  height: 58px;
  padding: 0;
  border: 1px solid var(--line);
  background: rgba(16,10,30,.96);
  color: var(--cyan);
  font: 500 1.25rem var(--mono);
  cursor: pointer;
  clip-path: polygon(0 0,100% 0,100% calc(100% - 8px),calc(100% - 8px) 100%,0 100%);
}

.sidebar-toggle:hover,
.sidebar-toggle:focus-visible {
  background: var(--cyan);
  color: var(--void);
  outline: none;
  box-shadow: 0 0 14px rgba(180,85,255,.25);
}

.sidebar-collapsed .course-shell {
  grid-template-columns: 0 minmax(0,1fr);
  gap: 0;
}

.sidebar-collapsed .course-sidebar {
  padding-left: 0;
  border-left: 0;
}

.sidebar-collapsed .course-sidebar-content {
  visibility: hidden;
  opacity: 0;
  pointer-events: none;
}

@media (max-width: 800px) {
  .sidebar-toggle {
    display: none;
  }

  .sidebar-collapsed .course-shell {
    grid-template-columns: 1fr;
    gap: 1rem;
  }

  .sidebar-collapsed .course-sidebar {
    padding-left: 1.2rem;
    border-left: 1px solid var(--line);
  }

  .sidebar-collapsed .course-sidebar-content {
    visibility: visible;
    opacity: 1;
    pointer-events: auto;
  }
}

@media (prefers-reduced-motion: reduce) {
  .course-shell,
  .course-sidebar {
    transition: none;
  }
}