.course-side-nav {
  position: fixed;
  top: 0;
  left: 0;
  width: 286px;
  height: 100vh;
  z-index: 50;
  background: rgba(255,255,255,0.96);
  border-right: 1px solid rgba(40, 54, 80, 0.10);
  box-shadow: 10px 0 30px rgba(35, 49, 80, 0.08);
  backdrop-filter: blur(10px);
  display: flex;
  flex-direction: column;
  transition: transform .22s ease, box-shadow .22s ease;
}
.course-side-nav.collapsed { transform: translateX(-246px); box-shadow: none; }
.course-side-nav-head {
  padding: 18px 16px 12px;
  border-bottom: 1px solid rgba(40, 54, 80, 0.08);
  display: flex;
  align-items: center;
  gap: 10px;
  justify-content: space-between;
}
.course-side-nav-title { font-size: 15px; font-weight: 800; color: #172033; letter-spacing: .02em; }
.course-side-nav-count { font-size: 12px; color: #6b778c; margin-top: 2px; }
.course-side-nav-toggle,
.course-side-nav-float {
  appearance: none;
  border: 0;
  cursor: pointer;
  border-radius: 999px;
  background: linear-gradient(135deg, #edf9f5, #f0faf7);
  color: #226b60;
  font-weight: 800;
  box-shadow: 0 6px 16px rgba(40, 54, 80, 0.10);
}
.course-side-nav-toggle { width: 34px; height: 34px; }
.course-side-nav-list { overflow-y: auto; padding: 12px 12px 18px; flex: 1; }
.course-side-nav-item {
  display: grid;
  grid-template-columns: 34px 1fr;
  gap: 8px;
  align-items: center;
  text-decoration: none;
  color: #31405a;
  border-radius: 14px;
  padding: 9px 10px;
  margin-bottom: 7px;
  background: rgba(246, 249, 253, 0.75);
  border: 1px solid rgba(52, 72, 106, 0.06);
  transition: background .18s ease, color .18s ease, transform .18s ease;
}
.course-side-nav-item:hover { background: #edf9f5; transform: translateX(2px); }
.course-side-nav-no {
  font-size: 12px;
  font-weight: 900;
  color: #3a9e8c;
  background: #fff;
  border-radius: 10px;
  text-align: center;
  padding: 5px 0;
}
.course-side-nav-text {
  font-size: 13px;
  line-height: 1.35;
  font-weight: 700;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.course-side-nav-item.active {
  background: linear-gradient(135deg, #edf9f5, #f0faf7);
  color: #0e314f;
  border-color: rgba(77,184,164,0.28);
  box-shadow: inset 4px 0 0 #4db8a4, 0 10px 22px rgba(77,184,164,0.10);
}
.course-side-nav-item.active .course-side-nav-no { color: #3a9e8c; }
body.has-course-side-nav .container { margin-left: 306px; }
.course-side-nav-float {
  display: none;
  position: fixed;
  left: 16px;
  bottom: 18px;
  z-index: 60;
  padding: 10px 14px;
  font-size: 14px;
}
body.screenshot-mode:not(.screenshot-with-side-nav) .course-side-nav,
body.screenshot-mode:not(.screenshot-with-side-nav) .course-side-nav-float { display: none !important; }
body.screenshot-mode:not(.screenshot-with-side-nav).has-course-side-nav .container { margin-left: auto !important; }
body.screenshot-mode.screenshot-with-side-nav .course-side-nav {
  display: flex !important;
  position: absolute;
  top: 0;
  left: 0;
  height: auto !important;
  min-height: 100vh;
  max-height: none !important;
  transform: none !important;
  box-shadow: 10px 0 30px rgba(35, 49, 80, 0.08);
}
body.screenshot-mode.screenshot-with-side-nav .course-side-nav-head {
  padding: 12px 12px 8px;
}
body.screenshot-mode.screenshot-with-side-nav .course-side-nav-title { font-size: 13px; }
body.screenshot-mode.screenshot-with-side-nav .course-side-nav-count { font-size: 10px; }
body.screenshot-mode.screenshot-with-side-nav .course-side-nav-list {
  overflow: visible !important;
  padding: 8px 8px 10px;
  flex: 0 0 auto;
}
body.screenshot-mode.screenshot-with-side-nav .course-side-nav-item {
  grid-template-columns: 30px 1fr;
  gap: 6px;
  padding: 5px 7px;
  margin-bottom: 4px;
  border-radius: 11px;
}
body.screenshot-mode.screenshot-with-side-nav .course-side-nav-no {
  font-size: 10px;
  padding: 4px 0;
  border-radius: 8px;
}
body.screenshot-mode.screenshot-with-side-nav .course-side-nav-text {
  font-size: 10.5px;
  line-height: 1.22;
  -webkit-line-clamp: 2;
}
body.screenshot-mode.screenshot-with-side-nav .course-side-nav-float { display: none !important; }
body.screenshot-mode.screenshot-with-side-nav.has-course-side-nav .container { margin-left: 306px !important; }
@media (max-width: 900px) {
  body.has-course-side-nav .container { margin-left: auto; }
  .course-side-nav { transform: translateX(-100%); width: min(84vw, 326px); }
  .course-side-nav.mobile-open { transform: translateX(0); }
  .course-side-nav.collapsed { transform: translateX(-100%); }
  .course-side-nav-float { display: inline-flex; align-items: center; gap: 6px; }
}