/* Three lessons, each with a visual suited to its evidence. */
.lesson-tabs { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: clamp(16px, 3vw, 40px); border-bottom: 1px solid var(--lab-line); }
.lesson-tab { display: flex; flex-direction: column; align-items: flex-start; justify-content: flex-start; gap: 3px; min-width: 0; min-height: 64px; padding: 12px 0 17px; border: 0; border-bottom: 2px solid transparent; background: transparent; color: var(--lab-muted); font: inherit; font-size: 17px; line-height: 1.35; text-align: left; white-space: normal; overflow-wrap: break-word; text-wrap: wrap; transition: color .15s, border-color .15s; }
.lesson-tab:hover { color: var(--lab-ink); }
.lesson-tab[aria-selected="true"] { border-bottom-color: var(--paper-accent); color: var(--lab-ink); }
/* All panels size one grid row, keeping the page steady when tabs change. */
.lesson-panels { display: grid; align-items: stretch; }
.lesson-panel { grid-area: 1 / 1; min-width: 0; padding-top: 28px; }
.lesson-panel[hidden] { display: block !important; visibility: hidden; pointer-events: none; }
.lesson-intro { margin-bottom: 24px; }
.lesson-intro p { max-width: 65ch; margin: 0; color: var(--lab-muted); font-size: var(--lab-subtitle-size); line-height: 1.65; text-wrap: pretty; }
.lesson-intro p + p { margin-top: 14px; }
/* Align the tracking description with its evidence. */
#lesson-panel-effort, #lesson-panel-time { width: min(100%, 960px); margin-inline: auto; }
.lesson-track-legend { position: absolute; z-index: 2; top: 16px; left: 16px; display: flex; flex-wrap: wrap; gap: 6px 20px; width: fit-content; max-width: calc(100% - 32px); margin: 0; padding: 8px 12px; border: 1px solid var(--lab-line); background: #22231fe8; backdrop-filter: blur(8px); color: var(--lab-ink); font-size: 14px; line-height: 1.5; pointer-events: none; }
.lesson-track-legend span { display: inline-flex; align-items: center; gap: 8px; white-space: nowrap; }
.lesson-track-legend span::before { content: ''; width: 13px; height: 13px; flex: 0 0 auto; border: 1.5px dashed #fff; border-radius: 50%; }
.lesson-track-legend span:last-child::before { border-style: solid; border-color: var(--ball-orange); }
.lesson-tracking { position: relative; width: min(100%, 960px); margin: 0 auto; aspect-ratio: 16 / 9; background: var(--lab-panel-deep); }
.lesson-video { display: block; width: 100%; height: auto; object-fit: contain; pointer-events: none; background: var(--lab-panel-deep); }
.lesson-tracking svg { position: absolute; inset: 0; width: 100%; height: 100%; pointer-events: none; overflow: hidden; }
.lesson-tracking svg[hidden] { display: none; }
.lesson-reference { fill: none; stroke: #fff; stroke-width: 2; stroke-dasharray: 5 5; }
.lesson-estimate { fill: none; stroke: var(--ball-orange); stroke-width: 3; }
.lesson-track-trail { fill: none; stroke: var(--ball-orange); stroke-width: 2; stroke-opacity: .7; stroke-linecap: round; stroke-linejoin: round; }
.lesson-error-line { stroke: var(--ball-orange); stroke-width: 1.5; stroke-dasharray: 4 5; }
.lesson-caption { max-width: 80ch; margin: 18px 0 0; color: var(--lab-muted); font-size: 15px; line-height: 1.65; text-wrap: pretty; }
.lesson-tracking + .lesson-caption { width: min(100%, 960px); margin-inline: auto; }

.lesson-time-layout { display: grid; grid-template-columns: minmax(0, 2.2fr) minmax(220px, 1fr); grid-template-areas: 'video metrics' 'timeline timeline'; gap: 24px 32px; }
.lesson-time-metrics { grid-area: metrics; display: flex; flex-direction: column; justify-content: center; gap: 32px; margin: 0; }
.lesson-time-metrics p { display: flex; flex-direction: column; gap: 8px; margin: 0; }
.lesson-time-metrics strong { display: block; font-size: clamp(32px, calc(22px + 2vw), 52px); font-weight: 400; line-height: 1.1; letter-spacing: -.045em; white-space: nowrap; font-variant-numeric: tabular-nums; }
.lesson-time-metrics strong span { padding-inline: .1em .35em; color: var(--lab-muted); font-size: .7em; letter-spacing: 0; vertical-align: baseline; }
.lesson-time-metrics strong span:last-child { padding-right: 0; }
.lesson-time-metrics p > span { color: var(--lab-muted); font-size: 15px; }
.lesson-collection-scope { margin: 0; color: var(--lab-muted); font-size: 14px; line-height: 1.65; text-wrap: pretty; }
.lesson-run-summaries { display: grid; margin: 24px 0 0; border-top: 1px solid var(--lab-line); }
.lesson-run-summaries > div { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: baseline; gap: 6px 18px; padding: 14px 0; border-bottom: 1px solid var(--lab-line); }
.lesson-run-summaries dt { color: var(--lab-muted); font-size: 14px; line-height: 1.65; }
.lesson-run-summaries dd { display: flex; flex-wrap: wrap; gap: 4px 18px; margin: 0; color: var(--lab-muted); font-size: 14px; line-height: 1.65; }
.lesson-run-summaries strong { color: var(--lab-ink); font-weight: 500; font-variant-numeric: tabular-nums; }
.lesson-collection-note { margin: 16px 0 0; color: var(--lab-muted); font-size: 13px; line-height: 1.65; text-wrap: pretty; }
.lesson-time-story { grid-area: timeline; min-width: 0; padding-top: 20px; border-top: 1px solid var(--lab-line); }
.lesson-timeline-heading { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: baseline; gap: 6px 18px; margin: 0 0 12px; }
.lesson-timeline-heading h4 { margin: 0; color: var(--lab-ink); font-size: 16px; font-weight: 400; line-height: 1.4; }
.lesson-timeline-heading p { margin: 0; color: var(--lab-muted); font-size: 14px; line-height: 1.5; font-variant-numeric: tabular-nums; }
.lesson-timeline-window { overflow-x: auto; scrollbar-width: thin; scrollbar-color: var(--lab-line) transparent; padding-bottom: 4px; }
.lesson-timeline { position: relative; height: 70px; min-width: 600px; margin-inline: 23px; }
.lesson-timeline::before { content: ''; position: absolute; top: 21px; left: 0; right: 0; height: 1px; background: var(--lab-line); }
.lesson-shot { position: absolute; top: 0; display: flex; justify-content: center; align-items: center; width: 44px; height: 44px; padding: 0; border: 0; background: transparent; color: var(--lab-muted); transform: translateX(-50%); font: inherit; font-size: 14px; }
.lesson-shot-number { display: grid; place-items: center; width: 29px; height: 29px; border: 1px solid var(--lab-line); border-radius: 50%; background: var(--paper-charcoal); transition: border-color .15s, color .15s, background .15s; }
.lesson-shot:hover .lesson-shot-number { border-color: var(--lab-muted); color: var(--lab-ink); }
.lesson-shot[aria-pressed="true"] .lesson-shot-number { border-color: var(--paper-accent); background: var(--paper-accent); color: var(--paper-accent-ink); }
.lesson-timeline-endpoint { position: absolute; bottom: 0; left: 0; transform: translateX(-50%); color: var(--lab-muted); font-size: 14px; font-variant-numeric: tabular-nums; }
.lesson-timeline-endpoint:last-of-type { left: 100%; }
.lesson-shot-preview { grid-area: video; min-width: 0; margin: 0; }
.lesson-shot-preview .lesson-video { aspect-ratio: 16 / 9; }
.lesson-shot-preview figcaption { margin-top: 16px; text-align: left; }
.lesson-shot-heading { display: flex; justify-content: space-between; align-items: baseline; gap: 20px; }
.lesson-shot-heading h4 { margin: 0; color: var(--lab-ink); font-size: 20px; font-weight: 400; line-height: 1.3; letter-spacing: -.02em; }
.lesson-shot-heading time { flex-shrink: 0; color: var(--lab-muted); font-size: 15px; font-variant-numeric: tabular-nums; }
.lesson-shot-preview figcaption p { max-width: 68ch; min-height: 3.3em; margin: 8px 0 0; color: var(--lab-muted); font-size: 15px; line-height: 1.65; text-wrap: pretty; }
.lesson-time-story > .lesson-caption { margin-top: 21px; }

.lesson-break-pair { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 20px; }
.lesson-break-pair figure { margin: 0; min-width: 0; }
.lesson-break-pair figcaption { margin-bottom: 14px; color: var(--lab-ink); font-size: 16px; }
.lesson-break-pair .lesson-video { aspect-ratio: 8 / 5; }
.lesson-model-media { position: relative; aspect-ratio: 8 / 5; background: transparent; }
.lesson-model-media > .lesson-video { width: 100%; height: 100%; background: transparent; }
.lesson-panel-status { margin-top: 16px; color: var(--lab-muted); font-size: 15px; }
.lesson-panel-status:empty { display: none; }

@media (max-width: 1100px) {
  .lesson-tabs { grid-template-columns: minmax(0, 1fr); grid-auto-rows: 1fr; gap: 0; border-top: 1px solid var(--lab-line); border-bottom: 0; }
  .lesson-tab { padding: 14px; border-bottom: 1px solid var(--lab-line); border-inline-start: 3px solid transparent; font-size: 16px; text-wrap: pretty; }
  .lesson-tab[aria-selected="true"] { border-bottom-color: var(--lab-line); border-inline-start-color: var(--paper-accent); }
}
@media (max-width: 767px) {
  .lesson-panel { padding-top: 24px; }
  .lesson-intro { margin-bottom: 20px; }
  .lesson-track-legend { top: 10px; left: 10px; max-width: calc(100% - 20px); padding: 6px 9px; font-size: 13px; gap: 5px 16px; }
  .lesson-time-layout { grid-template-columns: minmax(0, 1fr); grid-template-areas: 'metrics' 'video' 'timeline'; gap: 20px; }
  .lesson-time-metrics { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); align-items: start; gap: 20px; padding-bottom: 20px; border-bottom: 1px solid var(--lab-line); }
  .lesson-time-metrics p > span { font-size: 14px; }
  .lesson-shot-preview figcaption p { min-height: 6.6em; }
  .lesson-time-story > .lesson-caption { margin-top: 15px; }
  .lesson-break-pair { gap: 14px; }
  .lesson-break-pair figcaption { font-size: 15px; margin-bottom: 10px; }
  .lesson-caption { font-size: 15px; }
}
@media (max-width: 540px) {
  .lesson-break-pair { grid-template-columns: 1fr; gap: 22px; }
  .lesson-break-pair figcaption { font-size: 16px; }
}
@media (prefers-reduced-motion: reduce) {
  .lesson-tab, .lesson-shot-number { transition: none; }
}