:root {
  --student-accent: #4fd1c5;
  --student-accent-strong: #2bb9ad;
  --student-focus: #ffd166;
  --student-success: #5ed39b;
  --student-radius-sm: 10px;
  --student-radius-md: 16px;
  --student-radius-lg: 24px;
  --student-shadow: 0 24px 60px rgba(7, 17, 31, .22);
  --student-header-height: 72px;
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }

html,
body {
  min-height: 100%;
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.45;
}

body {
  min-width: 280px;
  padding: clamp(12px, 1.7vw, 28px);
}

button,
input,
select { font: inherit; }

button,
select {
  min-height: 42px;
  border-radius: var(--student-radius-sm);
}

button {
  cursor: pointer;
  transition: background-color .18s ease, border-color .18s ease, color .18s ease,
    box-shadow .18s ease, transform .18s ease;
}

button:hover { transform: translateY(-1px); }

button:focus-visible,
input:focus-visible,
select:focus-visible,
.stage:focus-visible,
.region-button:focus-visible,
.skip-link:focus-visible {
  outline: 3px solid var(--student-focus);
  outline-offset: 3px;
}

.skip-link {
  z-index: 1000;
  border-radius: 0 0 var(--student-radius-sm) var(--student-radius-sm);
}

.lesson-shell {
  width: min(1580px, 100%);
  margin: 0 auto;
}

.lesson-header {
  min-height: var(--student-header-height);
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  gap: 18px;
  margin: 0 0 14px;
  padding: 6px 4px;
}

.lesson-identity {
  min-width: 0;
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  column-gap: 13px;
  align-items: center;
}

.student-brand-mark {
  grid-row: 1 / 4;
  width: 42px;
  height: 42px;
  display: grid;
  place-items: center;
  border-radius: 13px;
  font-size: 12px;
  font-weight: 900;
  letter-spacing: -.02em;
  user-select: none;
}

.lesson-header .eyebrow {
  margin: 0 0 2px;
  font-size: 11px;
  font-weight: 800;
  letter-spacing: .13em;
  text-transform: uppercase;
}

.lesson-header h1 {
  min-width: 0;
  margin: 0;
  overflow: hidden;
  font-size: clamp(20px, 2vw, 30px);
  line-height: 1.15;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.slide-title {
  min-width: 0;
  margin: 3px 0 0;
  overflow: hidden;
  font-size: 13px;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.student-header-actions {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 8px;
}

#status {
  max-width: 190px;
  margin: 0 4px 0 0;
  overflow: hidden;
  font-size: 12px;
  text-align: right;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.student-header-button {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  font-weight: 750;
}

.student-header-button::before {
  content: "";
  width: 16px;
  height: 12px;
  border-top: 2px solid currentColor;
  border-bottom: 2px solid currentColor;
  box-shadow: inset 0 3px 0 transparent, inset 0 -3px 0 transparent;
}

.lesson-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(300px, 348px);
  gap: 14px;
  align-items: stretch;
  transition: grid-template-columns .22s ease;
}

.chapters-collapsed .lesson-grid { grid-template-columns: minmax(0, 1fr); }

.stage-column {
  min-width: 0;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  border-radius: var(--student-radius-lg);
  box-shadow: var(--student-shadow);
}

.stage {
  position: relative;
  display: grid;
  place-items: center;
  width: 100%;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  border: 0;
  border-radius: var(--student-radius-lg) var(--student-radius-lg) 0 0;
}

.source-fallback {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: contain;
}

#lessonCanvas {
  position: relative;
  z-index: 1;
  display: block;
  width: 100%;
  height: 100%;
}

.loading {
  z-index: 7;
  font-weight: 700;
  letter-spacing: .02em;
}

.stage-student-meta {
  position: absolute;
  z-index: 6;
  top: 14px;
  left: 14px;
  right: 14px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  pointer-events: none;
}

.stage-focus-pill,
.stage-focus-count {
  max-width: min(70%, 560px);
  padding: 7px 11px;
  overflow: hidden;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 800;
  line-height: 1.2;
  text-overflow: ellipsis;
  white-space: nowrap;
  backdrop-filter: blur(14px);
}

.stage-focus-count { flex: 0 0 auto; }

.captions {
  z-index: 8;
  max-width: 84%;
  padding: .55em .9em;
  border: 0;
  border-radius: 10px;
  font-size: clamp(15px, 2.1vw, 26px);
  line-height: 1.35;
  box-shadow: 0 8px 28px rgba(0, 0, 0, .35);
}

.transport {
  display: grid;
  gap: 10px;
  padding: 12px 14px 14px;
  border: 0;
}

.transport-row {
  display: flex;
  align-items: center;
  gap: 9px;
  flex-wrap: nowrap;
}

.transport-row + .transport-row { margin-top: 0; }

.primary-controls button {
  flex: 0 0 auto;
  min-height: 44px;
  padding-inline: 13px;
  font-weight: 780;
}

#playPause {
  min-width: 84px;
  border: 0;
  font-weight: 850;
  box-shadow: 0 8px 22px color-mix(in srgb, var(--student-accent) 28%, transparent);
}

#restart { min-width: 108px; }

.seek-label {
  flex: 1 1 auto;
  min-width: 100px;
  display: flex;
  align-items: center;
}

#seek {
  width: 100%;
  height: 20px;
  margin: 0;
  cursor: pointer;
  accent-color: var(--student-accent);
}

#timeOutput {
  flex: 0 0 auto;
  min-width: 104px;
  font-size: 12px;
  font-variant-numeric: tabular-nums;
  text-align: center;
}

#studentMoreControls {
  min-width: 44px;
  padding-inline: 11px;
}

.secondary-controls {
  min-height: 0;
  max-height: 0;
  padding: 0 4px;
  overflow: hidden;
  opacity: 0;
  transform: translateY(-6px);
  transition: max-height .22s ease, opacity .18s ease, transform .18s ease,
    padding .22s ease;
}

.secondary-open .secondary-controls {
  max-height: 96px;
  padding: 4px;
  opacity: 1;
  transform: none;
}

.secondary-controls label {
  display: flex;
  align-items: center;
  gap: 7px;
  font-size: 12px;
  white-space: nowrap;
}

.secondary-controls button,
.secondary-controls select { min-height: 38px; }

#volume { width: 76px; accent-color: var(--student-accent); }

.focus-panel {
  position: relative;
  min-width: 0;
  height: 100%;
  max-height: calc(100vh - 120px);
  display: flex;
  flex-direction: column;
  padding: 18px;
  overflow: hidden;
  border-radius: var(--student-radius-lg);
  box-shadow: var(--student-shadow);
}

.chapters-collapsed .focus-panel { display: none; }

.focus-heading {
  flex: 0 0 auto;
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 10px;
  align-items: start;
}

.focus-heading h2 {
  margin: 4px 0 6px;
  font-size: 18px;
  line-height: 1.25;
}

.focus-description {
  display: -webkit-box;
  margin: 0 0 14px;
  overflow: hidden;
  font-size: 13px;
  -webkit-box-orient: vertical;
  -webkit-line-clamp: 3;
}

#focusPosition {
  padding: 5px 8px;
  border-radius: 999px;
  font-size: 11px;
  font-weight: 850;
  white-space: nowrap;
}

.focus-actions {
  flex: 0 0 auto;
  display: grid;
  grid-template-columns: 1fr 1.25fr 1fr;
  gap: 7px;
}

.focus-actions button {
  min-width: 0;
  padding: 8px 6px;
  font-size: 12px;
  font-weight: 750;
}

.focus-list {
  flex: 1 1 auto;
  max-height: none;
  margin: 14px -5px 0 0;
  padding: 0 5px 0 0;
  overflow: auto;
  list-style: none;
  scrollbar-width: thin;
}

.focus-list li + li { margin-top: 7px; }

.focus-list button {
  width: 100%;
  min-height: 54px;
  display: grid;
  grid-template-columns: 28px minmax(0, 1fr);
  align-items: start;
  gap: 8px;
  padding: 10px;
  border-radius: 12px;
  text-align: left;
  line-height: 1.35;
}

.focus-state {
  min-width: 0;
  font-size: 12px;
  font-weight: 900;
  text-align: center;
}

.transcript-panel:not([hidden]) {
  position: fixed;
  z-index: 80;
  top: 20px;
  right: 20px;
  bottom: 20px;
  width: min(430px, calc(100vw - 40px));
  display: flex;
  flex-direction: column;
  padding: 20px;
  overflow: hidden;
  border-radius: var(--student-radius-lg);
  box-shadow: 0 30px 100px rgba(0, 0, 0, .5);
}

.panel-heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.panel-heading h2 { margin: 0; font-size: 20px; }

.transcript-list {
  flex: 1 1 auto;
  max-height: none;
  margin: 14px 0 0;
  overflow: auto;
}

.transcript-list button {
  padding: 12px;
  border-radius: 12px;
  line-height: 1.45;
}

.error-status {
  position: fixed;
  z-index: 120;
  left: 50%;
  bottom: 20px;
  width: min(680px, calc(100vw - 32px));
  margin: 0;
  transform: translateX(-50%);
}

@media (max-width: 1080px) {
  .lesson-grid { grid-template-columns: minmax(0, 1fr) 300px; }
  .secondary-open .secondary-controls { max-height: 160px; }
  .secondary-controls { flex-wrap: wrap; }
}

@media (max-width: 860px) {
  body { padding: 10px; }
  .lesson-header { grid-template-columns: minmax(0, 1fr) auto; }
  #status { display: none; }
  .lesson-grid { grid-template-columns: minmax(0, 1fr); }
  .focus-panel {
    max-height: 430px;
    grid-row: 2;
  }
  .chapters-collapsed .focus-panel { display: none; }
  .focus-list { max-height: 240px; }
}

@media (max-width: 640px) {
  body { padding: 0; }
  .lesson-header {
    min-height: 64px;
    margin: 0;
    padding: 9px 11px;
  }
  .student-brand-mark { width: 36px; height: 36px; border-radius: 11px; }
  .lesson-header h1 { font-size: 17px; }
  .slide-title { display: none; }
  .student-header-button { min-width: 42px; padding-inline: 10px; }
  .student-header-button span { display: none; }
  .stage-column,
  .stage { border-radius: 0; }
  .transport { padding: 9px; }
  .transport-row { gap: 6px; flex-wrap: wrap; }
  #playPause { min-width: 74px; }
  #restart { min-width: 44px; font-size: 0; }
  #restart::after { content: "Replay"; font-size: 12px; }
  #fullscreen { font-size: 0; }
  #fullscreen::after { content: "Full"; font-size: 12px; }
  .seek-label { order: 10; flex: 1 0 100%; }
  #timeOutput { min-width: 96px; }
  .secondary-open .secondary-controls { max-height: 250px; }
  .secondary-controls { align-items: stretch; }
  .secondary-controls label { width: auto; flex: 1 1 145px; justify-content: space-between; }
  .focus-panel { margin: 0 8px 10px; border-radius: 16px; }
  .transcript-panel:not([hidden]) {
    inset: auto 0 0;
    width: 100%;
    height: min(72vh, 620px);
    border-radius: 22px 22px 0 0;
  }
  .stage-student-meta { top: 8px; left: 8px; right: 8px; }
  .stage-focus-pill,
  .stage-focus-count { padding: 5px 8px; font-size: 10px; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    scroll-behavior: auto !important;
    transition-duration: .01ms !important;
    animation-duration: .01ms !important;
    animation-iteration-count: 1 !important;
  }
}

@media (forced-colors: active) {
  .stage-column,
  .focus-panel,
  .transcript-panel,
  button,
  select { border: 1px solid ButtonText; }
  .student-brand-mark { border: 2px solid ButtonText; }
}

:fullscreen .lesson-shell,
.lesson-shell:fullscreen {
  width: 100%;
  height: 100%;
  padding: 0;
}

:fullscreen .lesson-grid,
.lesson-shell:fullscreen .lesson-grid {
  height: 100%;
  grid-template-columns: minmax(0, 1fr) minmax(280px, 340px);
}

:fullscreen .chapters-collapsed .lesson-grid,
.lesson-shell:fullscreen.chapters-collapsed .lesson-grid {
  grid-template-columns: minmax(0, 1fr);
}

:fullscreen .stage-column,
.lesson-shell:fullscreen .stage-column {
  border-radius: 0;
}

:fullscreen .stage,
.lesson-shell:fullscreen .stage {
  flex: 1 1 auto;
  aspect-ratio: auto;
  border-radius: 0;
}