/* ==========================================================================
   Individual lesson page — "a digital workbench," not an LMS dashboard.
   Two-column shell: a sticky course/curriculum sidebar + the main lesson
   experience (video, tools, explainer, the interactive shelf exercise,
   Gaia's tip, checklist, completion). No cards/boxes/glassmorphism — the
   workshop photography, warm cream, black rules and one yellow accent ARE
   the interface. Shares .breadcrumb-bar/.course-section-title-style tokens
   with css/15-course-page.css where relevant.
   ========================================================================== */

.lesson-shell{
  display: grid;
  grid-template-columns: 300px 1fr;
  align-items: start;
  gap: clamp(2rem, 4vw, 3.5rem);
  padding: clamp(1.6rem, 3vw, 2.4rem) 0 clamp(4rem, 8vw, 6rem);
}

/* ---------------------------------------------------------------------- */
/* SIDEBAR                                                                 */
/* ---------------------------------------------------------------------- */
.lesson-sidebar{
  position: sticky;
  top: calc(var(--header-h) + 1.2rem);
  max-height: calc(100vh - var(--header-h) - 2.4rem);
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 1.6rem;
  padding-bottom: 1rem;
  scrollbar-width: thin;
}

.lesson-sidebar-back{
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: var(--font-body);
  font-weight: 700;
  font-size: 0.85rem;
  color: var(--color-dark);
  transition: color var(--dur-fast), gap var(--dur-fast);
}
.lesson-sidebar-back:hover{ color: var(--color-black); gap: 0.6rem; }
.lesson-sidebar-back svg{ width: 15px; height: 15px; flex: 0 0 auto; }

.lesson-sidebar-course{
  display: flex;
  align-items: center;
  gap: 0.9rem;
  padding-bottom: 1.3rem;
  border-bottom: 1.5px solid var(--color-black);
}
.lesson-sidebar-course-media{
  flex: 0 0 auto;
  width: 56px; height: 72px;
  border: 1.4px solid var(--color-black);
  border-radius: 8px;
  overflow: hidden;
}
.lesson-sidebar-course-media img{ width: 100%; height: 100%; object-fit: cover; }
.lesson-sidebar-course-num{
  font-family: var(--font-display);
  font-weight: var(--weight-display-heavy);
  font-size: 1.4rem;
  color: var(--color-black);
  line-height: 1;
  margin: 0 0 0.15rem;
}
.lesson-sidebar-course-title{
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1rem;
  color: var(--color-black);
  margin: 0;
}

.lesson-sidebar-progress-label{
  font-family: var(--font-body);
  font-weight: 700;
  font-size: 0.8rem;
  color: var(--color-muted);
  margin: 0 0 0.5rem;
}
.lesson-sidebar-progress-row{
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  font-family: var(--font-display);
  font-weight: 700;
  margin: 0 0 0.5rem;
}
.lesson-sidebar-progress-row .js-sidebar-progress-count{
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 0.82rem;
  color: var(--color-dark);
}
.lesson-sidebar-progress-row .js-sidebar-progress-percent{
  font-size: 1.3rem;
  color: var(--color-black);
}
/* Ruler-inspired progress bar: tick marks along the track, like a real
   measuring tape, not a generic rounded SaaS progress pill. */
.lesson-ruler{
  position: relative;
  height: 14px;
  border: 1.4px solid var(--color-black);
  background:
    repeating-linear-gradient(to right, var(--color-black) 0 1px, transparent 1px calc(100% / 11))
    left / 100% 100% no-repeat;
  background-color: transparent;
}
.lesson-ruler-fill{
  position: absolute;
  inset: 0 auto 0 0;
  width: 0%;
  background: var(--color-lime);
  transition: width 0.6s var(--ease-editorial);
}
[dir="rtl"] .lesson-ruler-fill{ inset: 0 0 0 auto; }

.lesson-curriculum{ display: flex; flex-direction: column; }
.lesson-curriculum-chapter + .lesson-curriculum-chapter{ margin-top: 1.1rem; }
.lesson-curriculum-chapter-title{
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 0.78rem;
  letter-spacing: 0.04em;
  color: var(--color-muted);
  text-transform: uppercase;
  margin: 0 0 0.5rem;
  padding-top: 0.9rem;
  border-top: 1px solid var(--color-line);
}
.lesson-curriculum-chapter:first-child .lesson-curriculum-chapter-title{ border-top: 0; padding-top: 0; }
.lesson-curriculum-list{
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
}
.lesson-curriculum-item{
  display: flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.5rem 0.55rem;
  border-radius: 6px;
  font-family: var(--font-body);
  font-size: 0.86rem;
  color: var(--color-muted);
  transition: background var(--dur-fast), color var(--dur-fast);
}
a.lesson-curriculum-item:hover{ background: rgba(17,17,17,0.05); color: var(--color-black); }
.lesson-curriculum-item .num{
  flex: 0 0 auto;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.78rem;
  color: var(--color-muted);
  min-width: 1.6em;
}
.lesson-curriculum-item .label{ flex: 1; line-height: 1.35; }
.lesson-curriculum-item .state{ flex: 0 0 auto; width: 16px; height: 16px; }
.lesson-curriculum-item .state svg{ width: 100%; height: 100%; color: var(--color-lime); }

.lesson-curriculum-item.is-current{
  background: var(--color-lime);
  color: var(--color-black);
  font-weight: 700;
}
.lesson-curriculum-item.is-current .num{ color: var(--color-black); }

.lesson-curriculum-item.is-upcoming{ color: rgba(107,102,93,0.7); cursor: default; }
.lesson-curriculum-item.is-upcoming .num{ color: rgba(107,102,93,0.7); }

.lesson-sidebar-help{
  border-top: 1.5px solid var(--color-black);
  padding-top: 1.3rem;
}
.lesson-sidebar-help-title{
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 0.95rem;
  margin: 0 0 0.35rem;
}
.lesson-sidebar-help-text{
  font-family: var(--font-body);
  font-size: 0.82rem;
  color: var(--color-muted);
  line-height: 1.4;
  margin: 0 0 0.8rem;
}
.lesson-sidebar-help-btn{
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.8rem;
  border-bottom: 1.4px solid var(--color-black);
  padding-bottom: 0.1rem;
  color: var(--color-black);
}

/* ---------------------------------------------------------------------- */
/* MOBILE CURRICULUM TRIGGER + DRAWER (hidden on desktop)                 */
/* ---------------------------------------------------------------------- */
.lesson-mobile-trigger{
  display: none;
}
.lesson-mobile-drawer{
  display: none;
}

/* ---------------------------------------------------------------------- */
/* MAIN CONTENT                                                            */
/* ---------------------------------------------------------------------- */
.lesson-main{ min-width: 0; }

.lesson-hero-header{ margin-bottom: clamp(1.6rem, 3vw, 2.2rem); }
.lesson-title{
  font-family: var(--font-display);
  font-weight: var(--weight-display-heavy);
  font-size: clamp(1.9rem, 3.6vw, 2.9rem);
  line-height: 1.06;
  letter-spacing: var(--tracking-display);
  color: var(--color-black);
  margin: 0 0 0.6rem;
  max-width: 22ch;
}
.lesson-duration{
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--color-muted);
}
.lesson-duration svg{ width: 15px; height: 15px; }

/* ---- Video ---- */
.lesson-video-frame{
  position: relative;
  aspect-ratio: 16/9;
  border-radius: 24px;
  overflow: hidden;
  background: #16130f;
  margin-bottom: clamp(2.2rem, 4vw, 3rem);
}
.lesson-video-el{
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  background: #16130f;
}
.lesson-video-veil{
  position: absolute;
  inset: 0;
  background: linear-gradient(to top, rgba(0,0,0,0.55) 0%, rgba(0,0,0,0) 45%);
  pointer-events: none;
}
.lesson-video-play-btn{
  position: absolute;
  top: 50%; left: 50%;
  transform: translate(-50%, -50%);
  width: 76px; height: 76px;
  border-radius: 50%;
  background: var(--color-lime);
  border: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  box-shadow: 0 12px 28px rgba(0,0,0,0.35);
  transition: transform var(--dur-fast) var(--ease-out);
}
.lesson-video-play-btn:hover{ transform: translate(-50%, -50%) scale(1.06); }
.lesson-video-play-btn svg{ width: 26px; height: 26px; color: var(--color-black); transform: translateX(-2px); }
.lesson-video-frame.is-playing .lesson-video-play-btn{ opacity: 0; pointer-events: none; }

.lesson-video-controls{
  position: absolute;
  inset-inline: 0;
  bottom: 0;
  display: flex;
  align-items: center;
  gap: 0.7rem;
  padding: 0.7rem 1rem;
  color: var(--color-white);
  opacity: 0;
  transform: translateY(6px);
  transition: opacity var(--dur-fast), transform var(--dur-fast);
}
.lesson-video-frame:hover .lesson-video-controls,
.lesson-video-frame.is-playing .lesson-video-controls{ opacity: 1; transform: translateY(0); }
.lesson-video-controls button{
  background: none; border: 0; padding: 0.2rem;
  color: var(--color-white);
  cursor: pointer;
  display: flex; align-items: center; justify-content: center;
}
.lesson-video-controls button svg{ width: 18px; height: 18px; }
.lesson-video-scrubber{
  position: relative;
  flex: 1;
  height: 3px;
  background: rgba(255,255,255,0.3);
  border-radius: 2px;
  cursor: pointer;
}
.lesson-video-scrubber-fill{
  position: absolute; inset: 0 auto 0 0; width: 0%;
  background: var(--color-lime);
  border-radius: 2px;
}
[dir="rtl"] .lesson-video-scrubber-fill{ inset: 0 0 0 auto; }
.lesson-video-time{
  font-family: var(--font-body);
  font-size: 0.78rem;
  font-weight: 600;
  white-space: nowrap;
  direction: ltr;
}
.lesson-video-note{
  position: absolute;
  bottom: 0.9rem; inset-inline-start: 1.1rem;
  font-family: var(--font-body);
  font-size: 0.78rem;
  color: rgba(255,255,255,0.65);
  pointer-events: none;
}
.lesson-video-frame.is-playing .lesson-video-note{ opacity: 0; }

/* ---- Numbered sections ---- */
.lesson-section{ margin-bottom: clamp(3rem, 6vw, 4.5rem); }
.lesson-section-head{
  display: flex;
  align-items: baseline;
  gap: 0.9rem;
  margin-bottom: 1.4rem;
}
.lesson-section-num{
  font-family: var(--font-display);
  font-weight: var(--weight-display-heavy);
  font-size: 1.1rem;
  color: var(--color-lime);
  -webkit-text-stroke: 1.2px var(--color-black);
}
.lesson-section-title{
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(1.2rem, 2vw, 1.55rem);
  letter-spacing: var(--tracking-display);
  color: var(--color-black);
  margin: 0;
}

/* ---- Tools strip ---- */
.lesson-tools-strip{
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  background: var(--color-black);
  border: 1.5px solid var(--color-black);
}
.lesson-tool-item{
  background: var(--color-bg);
  padding: 1.4rem 1rem;
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.7rem;
}
.lesson-tool-item-media{
  width: 100%;
  aspect-ratio: 1;
  display: flex;
  align-items: center;
  justify-content: center;
}
.lesson-tool-item-media img{
  max-width: 100%;
  max-height: 100%;
  object-fit: contain;
  filter: drop-shadow(0 6px 10px rgba(17,17,17,0.16));
}
.lesson-tool-item-media svg{ width: 42px; height: 42px; color: var(--color-black); }
/* Shown only until the real photo at this path is supplied (see
   js/lesson-content.js) — a neutral empty state, never a fake stand-in. */
.lesson-tool-item-media.is-missing{
  width: 100%; height: 100%;
  border: 1.4px dashed var(--color-line-strong);
  border-radius: 8px;
}
.lesson-tool-item-label{
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.88rem;
  color: var(--color-black);
}

/* ---- Explainer (editorial column, short scannable pieces) ---- */
.lesson-explainer-col{
  max-width: 680px;
}
.lesson-explainer-block{ margin: 0 0 1.7rem; }
.lesson-explainer-block:last-child{ margin-bottom: 0; }
.lesson-explainer-block-heading{
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1.08rem;
  color: var(--color-black);
  margin: 0 0 0.4rem;
}
.lesson-explainer-block-text{
  font-family: var(--font-body);
  font-size: 1.02rem;
  line-height: 1.65;
  color: var(--color-dark);
  margin: 0;
}
.lesson-explainer-media{
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  margin: 1.8rem 0 2rem;
  max-width: 680px;
}
.lesson-explainer-media figure{ margin: 0; }
.lesson-explainer-media img{
  width: 100%;
  aspect-ratio: 4/3;
  object-fit: cover;
  border-radius: 14px;
  display: block;
}
.lesson-explainer-media figcaption{
  font-family: var(--font-body);
  font-size: 0.78rem;
  color: var(--color-muted);
  margin-top: 0.45rem;
}

/* ---- Interactive shelf exercise — the hero interaction ---- */
.lesson-interactive-instruction{
  font-family: var(--font-body);
  font-size: 1.05rem;
  color: var(--color-dark);
  max-width: 60ch;
  margin: -0.6rem 0 2rem;
}
.shelf-exercise{
  background: var(--color-white);
  border: 1.5px solid var(--color-black);
  border-radius: 20px;
  padding: clamp(1.6rem, 3vw, 2.6rem);
}
.shelf-scale{
  display: flex;
  justify-content: space-between;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.85rem;
  color: var(--color-muted);
  padding: 0 1rem 0.6rem;
  direction: ltr;
}
.shelf-scale span:nth-child(3){ color: var(--color-black); }

.shelf-stage{
  position: relative;
  height: clamp(190px, 26vw, 260px);
  margin: 0 auto;
  max-width: 520px;
  touch-action: none;
}
.shelf-rig{
  position: absolute;
  left: 50%; top: 55%;
  width: 78%;
  transform: translate(-50%, -50%) rotate(-6deg);
  transform-origin: center center;
  will-change: transform;
}
.shelf-plank{
  height: 26px;
  background: linear-gradient(to bottom, #C99A68, #B07E4C);
  border: 1.5px solid var(--color-black);
  border-radius: 4px;
  box-shadow: 0 10px 18px rgba(17,17,17,0.18);
}
/* Real photographed level (assets/img/shelf-level.png, transparent cutout,
   no baked-in bubble — a plain filled vial) replaces the old CSS-drawn bar.
   The bubble stays a separate JS-driven element layered on top at the
   vial's measured position, since a real photo can't show a moving bubble
   on its own. */
.shelf-level{
  position: absolute;
  left: 50%; bottom: 100%;
  transform: translateX(-50%);
  margin-bottom: 6px;
  width: 62%;
  aspect-ratio: 1460 / 190;
  filter: drop-shadow(0 8px 14px rgba(17,17,17,0.18));
}
.shelf-level-photo{
  display: block;
  width: 100%;
  height: 100%;
  object-fit: contain;
}
/* Positioned to match the vial glass in shelf-level.png (measured: center
   51.16%/48.95%, size 17.12%/31.58% of the photo). */
.shelf-level-vial{
  position: absolute;
  left: 51.16%;
  top: 48.95%;
  width: 17.12%;
  height: 31.58%;
  transform: translate(-50%, -50%);
  border-radius: 6px;
  overflow: hidden;
}
.shelf-level-vial::before{
  content: '';
  position: absolute;
  top: 0; bottom: 0; left: 50%;
  width: 2px;
  transform: translateX(-50%);
  background: rgba(17,17,17,0.3);
}
.shelf-level-bubble{
  position: absolute;
  top: 50%; left: 50%;
  width: 32%; height: 62%;
  transform: translate(-50%, -50%);
  border-radius: 50%;
  background: radial-gradient(circle at 35% 30%, #fff, #cfead2 55%, #7fbf8e 100%);
  border: 1px solid rgba(17,17,17,0.3);
  transition: background var(--dur-fast);
}
.shelf-stage.is-level .shelf-level-bubble{
  background: radial-gradient(circle at 35% 30%, #fff, #d7f7dd 55%, #4fb567 100%);
}

.shelf-handle{
  position: absolute;
  top: 55%; left: 8%;
  width: 34px; height: 34px;
  margin-top: -17px;
  border-radius: 50%;
  background: var(--color-black);
  border: 3px solid var(--color-bg);
  box-shadow: 0 4px 10px rgba(17,17,17,0.3);
  cursor: grab;
  touch-action: none;
}
.shelf-handle:active{ cursor: grabbing; }
.shelf-handle::after{
  content: '';
  position: absolute;
  inset: 9px;
  border-radius: 50%;
  background: var(--color-lime);
}

.shelf-readout{
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1.2rem;
  margin-top: 1.6rem;
}
.shelf-readout-deg{
  font-family: var(--font-display);
  font-weight: var(--weight-display-heavy);
  font-size: clamp(1.6rem, 3vw, 2.1rem);
  color: var(--color-black);
  min-width: 3.5ch;
  text-align: center;
  direction: ltr;
}
.shelf-readout-status{
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1rem;
  color: var(--color-muted);
  opacity: 0;
  transform: scale(0.9);
  transition: opacity 0.25s var(--ease-out), transform 0.25s var(--ease-out);
}
.shelf-readout-status.is-success{
  opacity: 1;
  transform: scale(1);
  color: #2f8f45;
}
.shelf-readout-status svg{ width: 20px; height: 20px; }

/* ---- Gaia tip + checklist ---- */
.lesson-tip-checklist-row{
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: clamp(1.4rem, 3vw, 2.2rem);
  margin: clamp(3rem, 6vw, 4.5rem) 0;
  align-items: start;
}
.lesson-tip{
  display: flex;
  gap: 0.9rem;
  background: var(--color-lime);
  border-radius: 4px 18px 6px 20px / 14px 6px 18px 5px;
  padding: 1.3rem 1.4rem;
  transform: rotate(-0.5deg);
}
.lesson-tip-portrait{
  flex: 0 0 auto;
  width: 46px; height: 46px;
  border-radius: 50%;
  overflow: hidden;
  border: 1.5px solid var(--color-black);
}
.lesson-tip-portrait img{ width: 100%; height: 100%; object-fit: cover; }
.lesson-tip-label{
  font-family: var(--font-display);
  font-weight: var(--weight-display-heavy);
  font-size: 0.85rem;
  color: var(--color-black);
  margin: 0 0 0.3rem;
}
.lesson-tip-text{
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 0.95rem;
  line-height: 1.5;
  color: var(--color-black);
  margin: 0;
}

.lesson-checklist{ padding-top: 0.3rem; }
.lesson-checklist-title{
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1rem;
  color: var(--color-black);
  margin: 0 0 0.9rem;
}
.lesson-checklist-list{ list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 0.6rem; }
.lesson-checklist-item{
  display: flex; align-items: center; gap: 0.65rem;
  cursor: pointer; user-select: none;
}
.lesson-checklist-box{
  flex: 0 0 auto; width: 20px; height: 20px;
  border: 1.5px solid var(--color-black);
  display: flex; align-items: center; justify-content: center;
}
.lesson-checklist-box svg{ width: 13px; height: 13px; opacity: 0; color: var(--color-black); }
.lesson-checklist-item.is-checked .lesson-checklist-box{ background: var(--color-lime); }
.lesson-checklist-item.is-checked .lesson-checklist-box svg{ opacity: 1; }
.lesson-checklist-item.is-checked .lesson-checklist-text{ color: var(--color-muted); text-decoration: line-through; }
.lesson-checklist-text{ font-family: var(--font-body); font-size: 0.95rem; color: var(--color-dark); transition: color var(--dur-fast); }

/* ---- Bottom completion / nav bar ---- */
.lesson-complete-bar{
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
  padding-top: clamp(2rem, 4vw, 2.8rem);
  border-top: 1.5px solid var(--color-black);
}
.lesson-nav-prev{
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.92rem;
  color: var(--color-black);
}
.lesson-complete-btn{
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.95rem;
  padding: 0.9rem 1.8rem;
  background: var(--color-lime);
  color: var(--color-black);
  border: 1.5px solid var(--color-black);
  border-radius: 999px;
  transition: transform var(--dur-fast) var(--ease-out);
}
.lesson-complete-btn:hover{ transform: translateY(-1px); }
.lesson-complete-btn.is-done{ background: var(--color-black); color: var(--color-white); }
.lesson-complete-btn svg{ width: 18px; height: 18px; }

.lesson-nav-next{
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.9rem;
  padding: 0.75rem 1.3rem;
  border: 1.5px solid var(--color-black);
  border-radius: 999px;
  color: var(--color-black);
  transition: background var(--dur-fast);
}
a.lesson-nav-next:hover{ background: rgba(17,17,17,0.06); }
.lesson-nav-next.is-disabled{ color: var(--color-muted); opacity: 0.6; pointer-events: none; border-color: var(--color-line-strong); }
.lesson-nav-next-hint{ display: block; font-family: var(--font-body); font-weight: 500; font-size: 0.72rem; color: var(--color-muted); margin-top: 0.1rem; }

/* Scroll-in reveals on this page reuse the site's existing .reveal /
   .is-visible system (css/02-base.css + js/main.js initReveal) rather than
   a bespoke animation — after three rounds of custom scroll-triggered
   entrances misbehaving on the About section, the proven generic one wins. */

/* ---------------------------------------------------------------------- */
/* RESPONSIVE                                                              */
/* ---------------------------------------------------------------------- */
@media (max-width: 1100px){
  .lesson-shell{ grid-template-columns: 260px 1fr; }
}

@media (max-width: 900px){
  .lesson-shell{ display: block; padding-top: 1rem; }
  .lesson-sidebar{ display: none; }

  .lesson-mobile-trigger{
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: 100%;
    margin-bottom: 1.4rem;
    padding: 0.9rem 1.1rem;
    background: var(--color-white);
    border: 1.5px solid var(--color-black);
    border-radius: 12px;
    font-family: var(--font-display);
    font-weight: 700;
    font-size: 0.88rem;
    color: var(--color-black);
    cursor: pointer;
  }
  .lesson-mobile-trigger svg{ width: 16px; height: 16px; transition: transform var(--dur-fast); }
  .lesson-mobile-trigger[aria-expanded="true"] svg{ transform: rotate(180deg); }

  .lesson-mobile-drawer{
    display: block;
    position: fixed;
    inset: 0;
    z-index: 300;
    visibility: hidden;
    pointer-events: none;
  }
  .lesson-mobile-drawer-veil{
    position: absolute; inset: 0;
    background: rgba(17,17,17,0.45);
    opacity: 0;
    transition: opacity var(--dur-med);
  }
  .lesson-mobile-drawer-panel{
    position: absolute;
    inset-inline-start: 0; top: 0; bottom: 0;
    width: min(86vw, 340px);
    background: var(--color-bg);
    padding: 1.4rem 1.2rem 2rem;
    overflow-y: auto;
    transform: translateX(-100%);
    transition: transform var(--dur-med) var(--ease-out);
  }
  [dir="rtl"] .lesson-mobile-drawer-panel{ transform: translateX(100%); }
  .lesson-mobile-drawer.is-open{ visibility: visible; pointer-events: auto; }
  .lesson-mobile-drawer.is-open .lesson-mobile-drawer-veil{ opacity: 1; }
  .lesson-mobile-drawer.is-open .lesson-mobile-drawer-panel{ transform: translateX(0); }
  .lesson-mobile-drawer-close{
    display: flex; align-items: center; justify-content: center;
    width: 32px; height: 32px;
    margin-bottom: 1rem;
    border: 1.4px solid var(--color-black);
    border-radius: 50%;
    background: none;
    cursor: pointer;
  }
  .lesson-mobile-drawer-close svg{ width: 14px; height: 14px; }
  .lesson-mobile-drawer .lesson-sidebar{ display: flex; position: static; max-height: none; overflow: visible; }

  .lesson-tools-strip{ grid-template-columns: repeat(2, 1fr); }
  .lesson-explainer-media{ grid-template-columns: 1fr; }
  .lesson-tip-checklist-row{ grid-template-columns: 1fr; }
  .shelf-stage{ height: 220px; }
  .lesson-complete-bar{ flex-direction: column; align-items: stretch; }
  .lesson-complete-bar > *{ justify-content: center; text-align: center; }
}