body.lesson-player { margin: 0; background: #edf1f7; color: #192b43; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif; }
.lesson-player #quarto-header, .lesson-player #title-block-header, .lesson-player footer.footer, .lesson-player .page-footer { display: none; }
.lesson-player #quarto-content { display: block; padding: 0; }
.lesson-player #quarto-content main.content { margin: 0; padding: 0; max-width: none; width: 100%; }
.lesson-player [hidden] { display: none !important; }
.lesson-workspace { height: 100dvh; display: flex; flex-direction: column; }
.lesson-header { flex: 0 0 auto; padding: 6px 14px; background: #fff; border-bottom: 1px solid #dce2ec; display: flex; justify-content: space-between; align-items: center; gap: 16px; }
.lesson-header > div { display: grid; grid-template-columns: auto minmax(0, 1fr); column-gap: 16px; row-gap: 2px; align-items: center; min-width: 0; }
.lesson-back { grid-row: 1 / 3; }
.lesson-header a { color: #1755bc; font-size: 13px; text-decoration: none; }
.lesson-header a:hover { text-decoration: underline; }
.lesson-header #lesson-kicker { font-size: 11px; line-height: 1.2; font-weight: 700; text-transform: uppercase; letter-spacing: .08em; color: #67788e; margin: 0; }
.lesson-header h1 { font-size: 20px; line-height: 1.2; font-weight: 700; margin: 0; color: #152e4b; }
.lesson-header nav { display: flex; gap: 16px; white-space: nowrap; }
.lesson-toolbar { flex: 0 0 auto; display: flex; justify-content: space-between; align-items: center; gap: 12px; padding: 6px 14px; }
.view-options { display: inline-flex; border: 1px solid #cad5e5; border-radius: 7px; padding: 3px; background: #fff; }
.view-options button { border: 0; border-radius: 5px; background: transparent; color: #3d5372; font: 600 13px/1.4 -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif; padding: 6px 12px; cursor: pointer; }
.view-options button[aria-pressed="true"] { background: #1755bc; color: #fff; }
.view-options button:disabled { color: #8a96a7; cursor: default; }
.view-options button:focus-visible, .lesson-header a:focus-visible { outline: 3px solid #e3aa35; outline-offset: 3px; }
#lesson-status { color: #66758b; font-size: 12px; margin: 0; }
.hkust-ai-link { margin-left: auto; border: 1px solid #1755bc; border-radius: 6px; padding: 6px 12px; background: #fff; color: #1755bc; text-decoration: none; font: 600 13px/1.4 -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif; }
.hkust-ai-link:hover { background: #1755bc; color: #fff; }
.hkust-ai-link:focus-visible { outline: 3px solid #e3aa35; outline-offset: 3px; }
.lesson-panels { flex: 1; display: grid; grid-template-columns: minmax(0,1fr) minmax(0,1fr); gap: 10px; padding: 0 10px 8px; min-height: 0; }
.lesson-panels[data-view="video"], .lesson-panels[data-view="slides"] { grid-template-columns: minmax(0,1fr); }
.lesson-pane { display: flex; flex-direction: column; min-width: 0; overflow: hidden; border: 1px solid #d4ddea; border-radius: 9px; background: #fff; }
.pane-header { flex: 0 0 auto; display: flex; justify-content: space-between; gap: 12px; align-items: center; padding: 6px 12px; border-bottom: 1px solid #e4e9f0; }
.pane-header h2 { font-size: 13px; font-weight: 650; margin: 0; border: 0; padding: 0; }
.pane-header a { color: #1755bc; text-decoration: none; font-size: 11px; }
.pane-content { flex: 1; min-height: 0; }
.pane-content iframe { display: block; height: 100%; width: 100%; border: 0; min-height: 0; }
.video-pane .pane-content { background: #0d1727; }
.lesson-empty { padding: 30px; color: #617087; }
@media (max-width: 800px) {
  .lesson-workspace { height: auto; min-height: 100dvh; }
  .lesson-header { padding: 8px 12px; flex-wrap: wrap; gap: 8px; }
  .lesson-header > div { column-gap: 12px; }
  .lesson-header h1 { font-size: 18px; }
  .lesson-toolbar { padding: 6px 12px; flex-wrap: wrap; gap: 6px; }
  .view-options button { padding: 8px 10px; }
  #lesson-status { flex-basis: 100%; font-size: 11px; }
  .lesson-panels { flex: 0 0 auto; grid-template-columns: minmax(0,1fr); padding: 0 8px 8px; }
  .video-pane .pane-content, .video-pane iframe { min-height: 0; aspect-ratio: 16 / 9; height: auto; }
  .slides-pane .pane-content, .slides-pane iframe { height: 70dvh; min-height: 420px; }
}