/* One lesson only. Shared shell and accepted calm artwork remain untouched. */
main.pb-lesson.has-reading-sidebar {
  --reading-header: 72px;
  --reading-panel: 0px;
  display: grid;
  grid-template-columns: minmax(0, 1fr) 256px;
  gap: 32px;
  align-items: start;
  background: transparent;
  padding-block: 32px 20px;
}
.has-reading-sidebar .lesson-reading-card {
  min-width: 0;
  padding: 32px 40px 16px;
  background: #fff;
  border-radius: 16px;
  container: reading / inline-size;
  grid-column: 1;
  grid-row: 1;
}
.has-reading-sidebar .lesson-reading-card > .site-breadcrumb { margin: 0 0 32px; }
.has-reading-sidebar h1 { font-size: clamp(38px, 3.65vw, 52px); max-width: 790px; }
.has-reading-sidebar h2 { font-size: 36px; }
.has-reading-sidebar .pb-section { scroll-margin-top: calc(var(--reading-header) + var(--reading-panel) + 16px); }
.has-reading-sidebar .lesson-reading-sidebar {
  grid-column: 2;
  grid-row: 1;
  min-width: 0;
  position: sticky;
  top: calc(var(--reading-header) + 16px);
  align-self: start;
  color: #202024;
}
.has-reading-sidebar .lesson-toc { font-size: 15px; line-height: 1.4; }
.has-reading-sidebar .lesson-toc summary {
  display: flex;
  align-items: center;
  gap: 10px;
  min-height: 48px;
  padding: 12px 8px;
  list-style: none;
  pointer-events: none;
  font-weight: 700;
}
.has-reading-sidebar .lesson-toc summary::-webkit-details-marker { display: none; }
.has-reading-sidebar .lesson-toc-label { white-space: nowrap; }
.has-reading-sidebar .lesson-toc-current, .has-reading-sidebar .lesson-toc-chevron { display: none; }
.has-reading-sidebar .lesson-toc-panel { max-height: calc(100dvh - var(--reading-header) - 96px); overflow-y: auto; scrollbar-gutter: stable; overscroll-behavior: contain; }
.has-reading-sidebar .lesson-toc ol { list-style: none; margin: 0; padding: 0; }
.has-reading-sidebar .lesson-toc li { margin: 0; }
.has-reading-sidebar .lesson-toc a {
  display: flex;
  align-items: baseline;
  gap: 12px;
  min-height: 44px;
  padding: 12px 10px;
  border-left: 3px solid transparent;
  border-radius: 0 8px 8px 0;
  color: #44444b;
  text-decoration: none;
  overflow-wrap: break-word;
}
.has-reading-sidebar .lesson-toc a:hover { color: #503176; background: #ededf0; }
.has-reading-sidebar .lesson-toc a[aria-current="location"] {
  border-left-color: #684299;
  color: #503176;
  background: #ece7f3;
  font-weight: 700;
}
.has-reading-sidebar .lesson-toc-number { min-width: 1ch; font-size: 13px; color: #62626b; font-weight: 500; }
.has-reading-sidebar .lesson-sidebar-tools { margin-top: 24px; padding-top: 20px; border-top: 1px solid #d8d8de; }
.has-reading-sidebar .lesson-sidebar-tools p { padding: 0 13px 8px; color: #56565e; font-size: 13px; }
.has-reading-sidebar .lesson-sidebar-tools a { color: #684299; }
.has-reading-sidebar .lesson-sidebar-tools a span { margin-left: auto; }
.has-reading-sidebar :is(summary,a):focus-visible { outline: 3px solid #684299; outline-offset: 3px; }
.has-reading-sidebar .pb-section:focus { outline: none; }
.has-reading-sidebar .pb-section:focus-visible { outline: 2px solid #684299; outline-offset: 8px; }
@container reading (width < 700px) {
  .has-reading-sidebar .pb-stages { grid-template-columns: 1fr; }
  .has-reading-sidebar .pb-stage { display: grid; grid-template-columns: 56px minmax(0,1fr); align-items: center; gap: 14px; text-align: left; }
  .has-reading-sidebar .pb-stage img { width: 56px; height: 56px; margin: 0; }
  .has-reading-sidebar .pb-stage-arrow { width: 56px; height: 18px; display: grid; place-items: center; transform: rotate(90deg); margin-block: 2px; }
  main.pb-lesson.has-reading-sidebar #measurement .pb-check-pair { grid-template-columns: 14px minmax(0,1fr); gap: 4px 6px; }
  .has-reading-sidebar #measurement .pb-check-pair strong { grid-column: 1 / -1; }
}
@media (width < 1100px) {
  main.pb-lesson.has-reading-sidebar { grid-template-columns: minmax(0,1fr); gap: 16px; padding-top: 16px; }
  .has-reading-sidebar .lesson-reading-card { grid-column: 1; grid-row: 2; padding: 28px; }
  .has-reading-sidebar .lesson-reading-sidebar {
    grid-column: 1;
    grid-row: 1;
    top: var(--reading-header);
    z-index: 20;
    background: #f5f5f5;
    border: 1px solid #d8d8de;
    border-radius: 10px;
  }
  .has-reading-sidebar .lesson-toc summary { pointer-events: auto; cursor: pointer; padding: 10px 16px; }
  .has-reading-sidebar .lesson-toc-current { display: block; min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; font-size: 14px; color: #56565e; font-weight: 400; }
  .has-reading-sidebar .lesson-toc-chevron { display: block; margin-left: auto; font-size: 22px; line-height: 1; }
  .has-reading-sidebar .lesson-toc[open] .lesson-toc-chevron { transform: rotate(180deg); }
  .has-reading-sidebar .lesson-toc-panel { max-height: min(440px, calc(100dvh - var(--reading-header) - 88px)); padding: 0 10px 12px; border-top: 1px solid #d8d8de; }
  .has-reading-sidebar .lesson-sidebar-tools { margin-top: 12px; padding-top: 12px; }
  .has-reading-sidebar .lesson-reading-card > .site-breadcrumb { margin-bottom: 28px; }
  .has-reading-sidebar h1 { font-size: 48px; }
}
@media (width < 700px) {
  main.pb-lesson.has-reading-sidebar { --reading-header: 64px; padding-inline: 0; gap: 12px; }
  .has-reading-sidebar .lesson-reading-sidebar { margin-inline: 12px; }
  .has-reading-sidebar .lesson-reading-card { padding: 24px 18px 8px; border-radius: 12px 12px 0 0; }
  .has-reading-sidebar .lesson-toc summary { gap: 8px; padding-inline: 12px; }
  .has-reading-sidebar .lesson-toc-label { font-size: 13px; }
  .has-reading-sidebar .lesson-toc-current { font-size: 13px; }
  .has-reading-sidebar h1 { font-size: 37px; }
  .has-reading-sidebar h2 { font-size: 30px; }
}
@media (width < 360px) {
  .has-reading-sidebar h1 { font-size: 33px; }
  .has-reading-sidebar h2 { font-size: 28px; }
}
/* Rail stretches with the article; only TOC sticks, never the promotion. */
.has-reading-sidebar .lesson-sidebar-rail { grid-column: 2; grid-row: 1; min-width: 0; align-self: stretch; }
.has-reading-sidebar .lesson-reading-sidebar { background: #f5f5f5; z-index: 2; }
.has-reading-sidebar .lesson-intro-toc { margin: 28px 0 40px; border-block: 1px solid #dedee2; font-size: 16px; }
.has-reading-sidebar .lesson-intro-toc summary { min-height: 48px; display: flex; justify-content: space-between; align-items: center; padding: 14px 0; cursor: pointer; color: #503176; font-weight: 500; }
.has-reading-sidebar .lesson-intro-toc ol { list-style: none; padding: 0; margin: 0 0 16px; display: grid; grid-template-columns: 1fr 1fr; gap: 4px 18px; }
.has-reading-sidebar .lesson-intro-toc a { display: flex; align-items: center; gap: 12px; min-height: 44px; padding: 8px 0; text-decoration: none; color: #503176; }
.has-reading-sidebar .lesson-course-promo { margin: 0 0 24px; padding: 16px; border: 1px solid #d8d8de; border-radius: 12px; }
.has-reading-sidebar .lesson-course-art { width: min(100%, 240px); aspect-ratio: 3 / 2; margin-bottom: 16px; }
@media (width >= 1100px) {
  .has-reading-sidebar .lesson-toc-panel { max-height: calc(100dvh - var(--reading-toc-visible-top, 464px) - 64px); }
}
.has-reading-sidebar .lesson-course-art img { width: 100%; height: 100%; object-fit: cover; border-radius: 8px; }
.has-reading-sidebar .lesson-course-label { color: #56565e; font-size: 13px; margin-bottom: 8px; }
.has-reading-sidebar .lesson-course-promo h3 { font-size: 20px; line-height: 1.3; margin-bottom: 12px; }
.has-reading-sidebar .lesson-course-program { display: flex; align-items: center; min-height: 44px; color: #56565e; font-size: 13px; text-underline-offset: 3px; }
.has-reading-sidebar .lesson-course-link { min-height: 44px; display: flex; align-items: center; gap: 8px; color: #684299; font-size: 15px; text-underline-offset: 3px; }
@media (width < 1100px) {
  .has-reading-sidebar .lesson-sidebar-rail { display: contents; }
  .has-reading-sidebar .lesson-course-promo { grid-column: 1; grid-row: 3; max-width: 320px; margin: 12px 0 24px; }
  .has-reading-sidebar .lesson-intro-toc { display: none; }
}
@media (width < 700px) {
  .has-reading-sidebar .lesson-course-promo { margin-inline: 18px; }
}
/* Progressive enhancement: no JS leaves the full navigation in normal flow. */
.has-reading-sidebar:not(.reading-sidebar-ready) .lesson-reading-sidebar { position: static; }
@media (width < 1100px) {
  .has-reading-sidebar:not(.reading-sidebar-ready) .lesson-sidebar-rail { display: block; grid-column: 1; grid-row: 1; }
  .has-reading-sidebar:not(.reading-sidebar-ready) .lesson-course-promo { margin: 0 0 24px; }
  .has-reading-sidebar:not(.reading-sidebar-ready) .lesson-reading-sidebar { margin-inline: 0; }
}
@media print {
  main.pb-lesson.has-reading-sidebar { display: block; padding: 0; }
  .has-reading-sidebar .lesson-reading-sidebar { display: none; }
  .has-reading-sidebar .lesson-reading-card { padding: 0; }
}