/* lesson.css - styles for /learn lesson pages only
   All colors via CSS variables defined in ../../style.css
   No hardcoded color values. */

/* Page scaffold */
.lesson-page {
  min-height: 100vh;
  color: var(--text);
}

/* Learn index gradient background */
body.dark:not(.lesson-page) {
background:
  radial-gradient(
    ellipse 1200px 650px at 15% 0%,
    rgba(244, 114, 182, 0.05) 0%,
    transparent 65%
  ),
  radial-gradient(
    ellipse 1000px 550px at 85% 5%,
    rgba(96, 165, 250, 0.11) 0%,
    transparent 65%
  ),
  radial-gradient(
    ellipse 1100px 600px at 50% 100%,
    rgba(168, 85, 247, 0.09) 0%,
    transparent 70%
  ),
  radial-gradient(
    ellipse 900px 450px at 40% 15%,
    rgba(251, 191, 36, 0.07) 0%,
    transparent 60%
  ),
  radial-gradient(
    ellipse 700px 350px at 65% 25%,
    rgba(45, 212, 191, 0.12) 0%,
    transparent 60%
  ),
  #0f1721;

background-repeat: no-repeat;
background-attachment: fixed;
}

body:not(.dark):not(.lesson-page) {
  background:
    radial-gradient(
      ellipse 1200px 650px at 15% 0%,
      rgba(255, 130, 180, 0.08) 0%,
      transparent 65%
    ),
    radial-gradient(
      ellipse 1000px 550px at 85% 5%,
      rgba(120, 170, 255, 0.10) 0%,
      transparent 65%
    ),
    radial-gradient(
      ellipse 1100px 600px at 50% 100%,
      rgba(190, 140, 255, 0.08) 0%,
      transparent 70%
    ),
    radial-gradient(
      ellipse 900px 450px at 40% 15%,
      rgba(255, 210, 120, 0.08) 0%,
      transparent 60%
    ),
    radial-gradient(
      ellipse 700px 350px at 65% 25%,
      rgba(120, 220, 200, 0.09) 0%,
      transparent 60%
    ),
    #fafbfc;

  background-repeat: no-repeat;
  background-attachment: fixed;
}

/* Sandbox gradient button (Go to Sandbox) */
.btn-sandbox-gradient {
  background: linear-gradient(120deg, #1a7fcb, #6e3cba);
  color: #fff !important;
  border-color: color-mix(in oklab, #1a7fcb, #ffffff 22%);
  text-decoration: none;
}

body.dark .btn-sandbox-gradient {
  background: linear-gradient(120deg, #1568a8, #5a32a3);
  border-color: color-mix(in oklab, #1568a8, #ffffff 18%);
}

.btn-sandbox-gradient:hover {
  filter: brightness(1.12);
}

/* Hero tagline */
.learn-hero-tagline {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-top: 12px;
  padding: 7px 16px;
  border-radius: 999px;
  font-size: 0.88rem;
  font-weight: 500;
  color: var(--accent);
  background: color-mix(in oklab, var(--accent), transparent 88%);
  border: 1px solid color-mix(in oklab, var(--accent), transparent 60%);
  line-height: 1.5;
}

.learn-hero-tagline i {
  flex-shrink: 0;
  font-size: 0.8rem;
}

.lesson-wrap {
  max-width: 720px;
  margin: 0 auto;
  padding: 32px 20px 64px;
}

/* Breadcrumb */
.lesson-breadcrumb {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.82rem;
  color: var(--muted);
  margin-bottom: 24px;
  flex-wrap: wrap;
}

.lesson-breadcrumb a {
  color: var(--accent);
  text-decoration: none;
  transition: color 120ms ease;
}

.lesson-breadcrumb a:hover {
  color: var(--accent-2);
}

.lesson-breadcrumb .sep {
  color: var(--border);
}

.lesson-breadcrumb .current {
  color: var(--text);
  font-weight: 500;
}

/* Lesson meta (part + read time) */
.lesson-meta {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 14px;
  flex-wrap: wrap;
}

.lesson-part-label {
  display: inline-block;
  border-radius: 999px;
  padding: 4px 12px;
  font-size: 0.74rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  background: linear-gradient(120deg, color-mix(in oklab, var(--accent), transparent 80%), color-mix(in oklab, var(--accent-2), transparent 80%));
  border: 1px solid color-mix(in oklab, var(--accent), transparent 55%);
  color: var(--accent);
}

.lesson-read-time {
  font-size: 0.8rem;
  color: var(--muted);
  display: flex;
  align-items: center;
  gap: 5px;
}

/* Title + subtitle */
.lesson-title {
  font-size: 2rem;
  font-weight: 700;
  line-height: 1.2;
  margin: 0 0 14px;
  letter-spacing: -0.01em;
}

.lesson-subtitle {
  font-size: 1.05rem;
  color: var(--muted);
  line-height: 1.6;
  margin: 0 0 36px;
  border-left: 3px solid var(--accent);
  padding-left: 14px;
}

/* Content sections */
.lesson-section {
  margin-bottom: 32px;
}

.lesson-section h2 {
  font-size: 1.2rem;
  font-weight: 700;
  margin: 0 0 12px;
  color: var(--text);
}

.lesson-section p {
  font-size: 0.97rem;
  line-height: 1.72;
  color: var(--text);
  margin: 0 0 14px;
}

.lesson-section p:last-child {
  margin-bottom: 0;
}

.lesson-section strong {
  color: var(--text);
  font-weight: 700;
}

/* Highlight callout inside a section */
.lesson-callout {
  border-left: 3px solid var(--accent-2);
  background: color-mix(in oklab, var(--accent-2), transparent 91%);
  border-radius: 0 10px 10px 0;
  padding: 12px 16px;
  margin: 16px 0;
  font-size: 0.93rem;
  line-height: 1.6;
  color: var(--text);
}

/* Sandbox demo callout */
.lesson-demo-callout {
  border: 1px solid color-mix(in oklab, var(--accent), transparent 45%);
  border-radius: 14px;
  background: color-mix(in oklab, var(--accent), transparent 91%);
  padding: 20px;
  margin: 28px 0;
}

.demo-callout-label {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 10px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.demo-callout-title {
  font-size: 1rem;
  font-weight: 700;
  margin: 0 0 12px;
  color: var(--text);
}

.demo-steps {
  list-style: none;
  padding: 0;
  margin: 0 0 16px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.demo-steps li {
  display: flex;
  gap: 10px;
  align-items: flex-start;
  font-size: 0.9rem;
  line-height: 1.55;
  color: var(--text);
}

.demo-steps li::before {
  content: attr(data-n);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 22px;
  height: 22px;
  border-radius: 999px;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  color: #fff;
  font-size: 0.72rem;
  font-weight: 700;
  flex-shrink: 0;
  margin-top: 1px;
}

/* Lesson sandbox iframe */
.lesson-sandbox {
  width: 100%;
  height: 420px;
  border-radius: 14px;
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
  display: block;
  background: var(--panel);
}

/* Knowledge check */
.lesson-check {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 22px;
  margin: 36px 0;
  box-shadow: var(--shadow);
}

.check-label {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--accent-2);
  margin-bottom: 10px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.check-question {
  font-size: 1.02rem;
  font-weight: 600;
  line-height: 1.5;
  margin: 0 0 16px;
  color: var(--text);
}

.check-options {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-bottom: 14px;
}

.check-option {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  width: 100%;
  text-align: left;
  padding: 12px 14px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--panel-alt);
  color: var(--text);
  font-family: inherit;
  font-size: 0.93rem;
  line-height: 1.5;
  cursor: pointer;
  transition: border-color 140ms ease, background 140ms ease, transform 100ms ease;
}

.check-option:hover:not(:disabled) {
  border-color: var(--accent-2);
  transform: translateY(-1px);
}

.check-option:disabled {
  cursor: default;
  transform: none;
}

.check-option.correct {
  border-color: var(--accent);
  background: color-mix(in oklab, var(--accent), transparent 88%);
  color: var(--text);
}

.check-option.incorrect {
  border-color: #e34d4d;
  background: color-mix(in oklab, #e34d4d, transparent 90%);
  color: var(--text);
  opacity: 0.7;
}

.check-option.revealed {
  border-color: var(--accent);
  background: color-mix(in oklab, var(--accent), transparent 88%);
}

.check-feedback {
  font-size: 0.88rem;
  line-height: 1.55;
  color: var(--muted);
  padding: 10px 12px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: color-mix(in oklab, var(--panel-alt), transparent 20%);
  display: none;
}

.check-feedback.visible {
  display: block;
}

.check-feedback.correct-feedback {
  border-color: color-mix(in oklab, var(--accent), transparent 40%);
  background: color-mix(in oklab, var(--accent), transparent 90%);
  color: var(--text);
}

.check-feedback.incorrect-feedback {
  border-color: color-mix(in oklab, #e34d4d, transparent 40%);
  background: color-mix(in oklab, #e34d4d, transparent 92%);
  color: var(--text);
}

/* Score badge (shown after MCQ answer) */
.lesson-score-badge {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  margin-top: 12px;
  padding: 4px 14px;
  border-radius: 999px;
  font-size: 0.85rem;
  font-weight: 700;
  font-family: var(--mono, monospace);
  animation: badge-pop 280ms cubic-bezier(0.34, 1.56, 0.64, 1);
}

.lesson-score-badge.pts-correct {
  background: color-mix(in oklab, var(--accent), transparent 84%);
  border: 1px solid color-mix(in oklab, var(--accent), transparent 40%);
  color: var(--accent);
}

.lesson-score-badge.pts-partial {
  background: color-mix(in oklab, #f59e0b, transparent 85%);
  border: 1px solid color-mix(in oklab, #f59e0b, transparent 50%);
  color: #c77d10;
}

body.dark .lesson-score-badge.pts-partial {
  color: #fbbf24;
}

@keyframes badge-pop {
  from { opacity: 0; transform: scale(0.7); }
  to   { opacity: 1; transform: scale(1); }
}

/* Running score chip in topbar */
.running-score-chip {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 4px 12px;
  border-radius: 999px;
  font-size: 0.8rem;
  font-weight: 600;
  border: 1px solid color-mix(in oklab, var(--accent-2), transparent 50%);
  background: color-mix(in oklab, var(--accent-2), transparent 88%);
  color: var(--accent-2);
  white-space: nowrap;
}

/* Takeaway block */
.lesson-takeaway {
  border: 1px solid color-mix(in oklab, var(--accent-2), transparent 45%);
  border-left: 4px solid var(--accent-2);
  border-radius: 0 14px 14px 0;
  background: color-mix(in oklab, var(--accent-2), transparent 91%);
  padding: 18px 20px;
  margin: 32px 0;
}

.takeaway-label {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--accent-2);
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.takeaway-text {
  font-size: 1rem;
  font-weight: 600;
  line-height: 1.6;
  color: var(--text);
  margin: 0;
}

/* Lesson navigation */
.lesson-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  margin-top: 40px;
  flex-wrap: wrap;
}

.lesson-nav .btn {
  min-width: 140px;
}

.lesson-nav .btn-nav-next {
  margin-left: auto;
}

/* Learn index page */
.learn-hero {
  padding: 20px 0 8px;
  margin-bottom: 4px;
}

.learn-hero h1 {
  font-size: 1.6rem;
  font-weight: 700;
  margin: 0 0 8px;
  letter-spacing: -0.01em;
}

.learn-hero p {
  font-size: 0.92rem;
  color: var(--muted);
  margin: 0;
  line-height: 1.5;
}

.learn-progress-bar-wrap {
  margin: 14px 0 12px;
  background: color-mix(in oklab, var(--border), transparent 25%);
  border-radius: 999px;
  height: 8px;
  overflow: hidden;
}

.learn-progress-bar-fill {
  height: 100%;
  border-radius: 999px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  transition: width 600ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.learn-carousel {
  position: relative;
}

.learn-part {
  display: none;
  margin-bottom: 8px;
}

.learn-part.active {
  display: block;
  animation: learnPartIn 240ms ease;
}

@keyframes learnPartIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: none; }
}

.learn-carousel-nav {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 18px;
  margin: 4px 0 16px;
}

.learn-carousel-dots {
  display: flex;
  align-items: center;
  gap: 9px;
}

.learn-dot {
  width: 9px;
  height: 9px;
  padding: 0;
  border: none;
  border-radius: 999px;
  background: var(--border);
  cursor: pointer;
  transition: background 150ms ease, transform 150ms ease;
}

.learn-dot:hover {
  transform: scale(1.2);
}

.learn-dot.active {
  transform: scale(1.3);
}

.learn-dot:nth-child(1).active { background: var(--accent); }
.learn-dot:nth-child(2).active { background: var(--accent-2); }
.learn-dot:nth-child(3).active { background: var(--accent-3); }

.learn-part-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 10px;
}

.learn-part-title {
  font-size: 1.1rem;
  font-weight: 700;
  margin: 0;
  color: var(--part-color, var(--text));
}

.learn-part-badge {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--part-color, var(--muted));
  background: color-mix(in oklab, var(--part-color, var(--muted)), transparent 88%);
  border: 1px solid color-mix(in oklab, var(--part-color, var(--muted)), transparent 55%);
  border-radius: 999px;
  padding: 3px 10px;
}

.learn-lessons-grid {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.learn-lesson-card {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 10px 16px;
  border-radius: 12px;
  border: 1px solid var(--border);
  border-left: 3px solid color-mix(in oklab, var(--part-color, var(--border)), transparent 55%);
  background: var(--panel);
  text-decoration: none;
  color: var(--text);
  transition: border-color 140ms ease, transform 120ms ease, box-shadow 140ms ease;
}

.learn-lesson-card:hover {
  border-color: var(--part-color, var(--accent-2));
  transform: translateY(-1px);
  box-shadow: 0 4px 16px rgba(0,0,0,0.12);
}

.learn-lesson-num {
  font-family: "IBM Plex Mono", monospace;
  font-size: 0.78rem;
  font-weight: 700;
  color: color-mix(in oklab, var(--part-color, var(--muted)), var(--muted) 35%);
  min-width: 28px;
}

.learn-lesson-info {
  flex: 1;
  min-width: 0;
}

.learn-lesson-title {
  font-size: 0.95rem;
  font-weight: 600;
  margin: 0 0 2px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.learn-lesson-time {
  font-size: 0.78rem;
  color: var(--muted);
}

.learn-lesson-status {
  width: 22px;
  height: 22px;
  border-radius: 999px;
  border: 2px solid var(--border);
  background: var(--panel-alt);
  display: grid;
  place-items: center;
  flex-shrink: 0;
  transition: border-color 200ms ease, background 200ms ease;
}

.learn-lesson-status.done {
  border-color: var(--accent);
  background: color-mix(in oklab, var(--accent), transparent 78%);
  color: var(--accent);
}

.learn-lesson-status.done::after {
  content: "";
  width: 8px;
  height: 5px;
  border-left: 2px solid var(--accent);
  border-bottom: 2px solid var(--accent);
  transform: rotate(-45deg) translateY(-1px);
  display: block;
}

/* Responsive */
@media (max-width: 640px) {
  .lesson-wrap {
    padding: 20px 14px 48px;
  }

  .lesson-title {
    font-size: 1.5rem;
  }

  .lesson-sandbox {
    height: 360px;
  }

  .lesson-nav {
    flex-direction: column;
    align-items: stretch;
  }

  .lesson-nav .btn {
    min-width: 0;
    width: 100%;
    justify-content: center;
  }

  .lesson-nav .btn-nav-next {
    margin-left: 0;
  }

  .learn-lesson-title {
    white-space: normal;
  }
}

/* Congratulations page */
.congrats-hero {
  text-align: center;
  padding: 48px 0 36px;
}

.congrats-icon {
  font-size: 3.5rem;
  color: var(--accent-2);
  margin-bottom: 20px;
  display: block;
  animation: congrats-pop 0.5s cubic-bezier(0.34, 1.56, 0.64, 1) both;
}

@keyframes congrats-pop {
  from { transform: scale(0.5); opacity: 0; }
  to   { transform: scale(1);   opacity: 1; }
}

.congrats-badge {
  display: inline-block;
  border-radius: 999px;
  padding: 4px 14px;
  font-size: 0.74rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  background: linear-gradient(120deg, color-mix(in oklab, var(--accent), transparent 80%), color-mix(in oklab, var(--accent-2), transparent 80%));
  border: 1px solid color-mix(in oklab, var(--accent), transparent 55%);
  color: var(--accent);
  margin-bottom: 18px;
}

.congrats-title {
  font-size: 2.6rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin: 0 0 14px;
  line-height: 1.15;
}

.congrats-subtitle {
  font-size: 1.05rem;
  color: var(--muted);
  line-height: 1.65;
  max-width: 520px;
  margin: 0 auto 28px;
}

.congrats-score-display {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 22px;
  border-radius: 999px;
  font-size: 1.05rem;
  font-weight: 700;
  border: 1px solid color-mix(in oklab, var(--accent-2), transparent 40%);
  background: color-mix(in oklab, var(--accent-2), transparent 86%);
  color: var(--accent-2);
}

.congrats-mastered {
  margin: 0 0 36px;
  border: 1px solid var(--border);
  border-radius: 16px;
  background: var(--panel);
  box-shadow: var(--shadow);
  padding: 24px 28px;
}

.congrats-mastered h2 {
  font-size: 1rem;
  font-weight: 700;
  margin: 0 0 16px;
  color: var(--text);
}

.congrats-mastered ul {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px 20px;
}

.congrats-mastered li {
  font-size: 0.92rem;
  color: var(--muted);
  display: flex;
  align-items: center;
  gap: 8px;
}

.congrats-mastered li i {
  color: var(--accent);
  font-size: 0.75rem;
  flex-shrink: 0;
}

.congrats-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
  padding-top: 8px;
}

.congrats-actions .btn {
  min-width: 160px;
  justify-content: center;
}

@media (max-width: 480px) {
  .congrats-title { font-size: 1.9rem; }
  .congrats-mastered ul { grid-template-columns: 1fr; }
  .congrats-actions .btn { width: 100%; }
}

.btn {
  text-decoration: none;
  font-family: "Space Grotesk", sans-serif;
}
/* Gradient nav buttons (matching root Guide button style) */
.btn-nav-next {
  background: linear-gradient(120deg, var(--accent), var(--accent-2)) !important;
  color: #fff !important;
  border-color: color-mix(in oklab, var(--accent-2), #ffffff 20%) !important;
}
body.dark .btn-nav-next {
  background: linear-gradient(120deg, #23936f, #3e79cf) !important;
  border-color: color-mix(in oklab, #3e79cf, #ffffff 16%) !important;
}
.btn-nav-next:hover {
  filter: brightness(1.1);
}

/* Expand / Accordion cards */
.expand-cards {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin: 20px 0;
}
.expand-card {
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--panel);
  overflow: hidden;
  transition: border-color 150ms ease;
}
.expand-card.open { border-color: var(--accent-2); }
.expand-card-header {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 16px;
  cursor: pointer;
  user-select: none;
}
.expand-card-header:hover { background: color-mix(in oklab, var(--panel-alt), transparent 30%); }
.expand-card-icon {
  width: 36px; height: 36px;
  border-radius: 10px;
  display: grid; place-items: center;
  font-size: 1.1rem; flex-shrink: 0;
  background: color-mix(in oklab, var(--accent-2), transparent 82%);
  color: var(--accent-2);
}
.expand-card-title { flex: 1; font-weight: 700; font-size: 0.97rem; color: var(--text); }
.expand-card-subtitle { font-size: 0.82rem; color: var(--muted); margin-top: 2px; }
.expand-card-chevron {
  color: var(--muted); font-size: 0.85rem;
  transition: transform 240ms cubic-bezier(0.2,0.8,0.2,1);
  flex-shrink: 0;
}
.expand-card.open .expand-card-chevron { transform: rotate(180deg); }
.expand-card-body { max-height: 0; overflow: hidden; transition: max-height 300ms cubic-bezier(0.2,0.8,0.2,1); }
.expand-card.open .expand-card-body { max-height: 700px; }
.expand-card-inner {
  padding: 12px 16px 16px;
  font-size: 0.93rem; line-height: 1.68;
  color: var(--text);
  border-top: 1px solid var(--border);
}
.expand-card-inner p { margin: 0 0 10px; }
.expand-card-inner p:last-child { margin-bottom: 0; }

/* Flowchart */
.lesson-flowchart {
  display: flex; flex-direction: column; align-items: center;
  margin: 24px 0;
}
.fc-node {
  padding: 14px 20px; border-radius: 12px;
  border: 1px solid var(--border); background: var(--panel);
  text-align: center; max-width: 340px; width: 100%;
  box-shadow: var(--shadow);
  transition: border-color 140ms ease;
}
.fc-node:hover { border-color: var(--accent-2); }
.fc-node-label {
  font-size: 0.68rem; font-weight: 700; letter-spacing: 0.05em;
  text-transform: uppercase; color: var(--accent); margin-bottom: 3px;
}
.fc-node-title { font-size: 1rem; font-weight: 700; color: var(--text); }
.fc-node-desc { font-size: 0.83rem; color: var(--muted); line-height: 1.5; margin-top: 5px; }
.fc-arrow {
  width: 2px; height: 28px;
  background: linear-gradient(180deg, var(--accent), var(--accent-2));
  position: relative; margin: 0 auto;
}
.fc-arrow::after {
  content: ""; position: absolute;
  bottom: -7px; left: 50%; transform: translateX(-50%);
  width: 0; height: 0;
  border-left: 6px solid transparent; border-right: 6px solid transparent;
  border-top: 8px solid var(--accent-2);
}
.fc-row {
  display: flex; justify-content: center; gap: 10px; width: 100%;
  flex-wrap: wrap;
}

/* Quantum Timeline */
.lesson-timeline { position: relative; margin: 24px 0; padding-left: 28px; }
.lesson-timeline::before {
  content: ""; position: absolute; left: 8px; top: 0; bottom: 0;
  width: 2px;
  background: linear-gradient(180deg, var(--accent), var(--accent-2), color-mix(in oklab, var(--accent-2), transparent 60%));
  border-radius: 2px;
}
.tl-item { position: relative; padding: 0 0 20px 16px; }
.tl-item:last-child { padding-bottom: 0; }
.tl-dot {
  position: absolute; left: -24px; top: 4px;
  width: 14px; height: 14px; border-radius: 999px;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  border: 2px solid var(--bg); box-shadow: 0 0 0 2px var(--accent);
}
.tl-year {
  font-size: 0.72rem; font-weight: 700; letter-spacing: 0.06em;
  text-transform: uppercase; color: var(--accent-2); margin-bottom: 3px;
  font-family: "IBM Plex Mono", monospace;
}
.tl-title { font-size: 0.95rem; font-weight: 700; color: var(--text); margin-bottom: 3px; }
.tl-desc { font-size: 0.86rem; color: var(--muted); line-height: 1.55; }

/* Comparison grid (classical vs quantum) */
.lesson-compare-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin: 20px 0; }
.compare-col { border: 1px solid var(--border); border-radius: 12px; background: var(--panel); overflow: hidden; }
.compare-col-head {
  padding: 10px 14px; font-size: 0.78rem; font-weight: 700;
  letter-spacing: 0.04em; text-transform: uppercase;
  display: flex; align-items: center; gap: 7px;
}
.compare-col.classical .compare-col-head { background: color-mix(in oklab, var(--muted), transparent 85%); color: var(--muted); }
.compare-col.quantum .compare-col-head { background: color-mix(in oklab, var(--accent), transparent 83%); color: var(--accent); }
.compare-col-body { padding: 12px 14px; display: flex; flex-direction: column; gap: 7px; }
.compare-row { display: flex; align-items: flex-start; gap: 7px; font-size: 0.87rem; line-height: 1.5; color: var(--text); }
.compare-row i { margin-top: 2px; flex-shrink: 0; font-size: 0.75rem; }
.compare-col.classical .compare-row i { color: var(--muted); }
.compare-col.quantum .compare-row i { color: var(--accent); }

/* Probability slider visualizer */
.prob-slider-wrap { background: var(--panel); border: 1px solid var(--border); border-radius: 14px; padding: 20px; margin: 24px 0; }
.prob-slider-label {
  font-size: 0.72rem; font-weight: 700; letter-spacing: 0.05em;
  text-transform: uppercase; color: var(--accent-2); margin-bottom: 12px;
  display: flex; align-items: center; gap: 6px;
}
.prob-bars { display: flex; gap: 12px; margin-bottom: 16px; }
.prob-bar-group { flex: 1; display: flex; flex-direction: column; align-items: center; gap: 5px; }
.prob-bar-track { width: 100%; height: 12px; border-radius: 999px; background: var(--panel-alt); overflow: hidden; }
.prob-bar-fill { height: 100%; border-radius: 999px; transition: width 80ms ease; }
.prob-bar-fill.alpha { background: linear-gradient(90deg, var(--accent), color-mix(in oklab, var(--accent), var(--accent-2) 50%)); }
.prob-bar-fill.beta  { background: linear-gradient(90deg, var(--accent-2), color-mix(in oklab, var(--accent-2), #b078ff 60%)); }
.prob-bar-label { font-size: 0.8rem; font-weight: 700; font-family: "IBM Plex Mono", monospace; color: var(--text); }
.prob-bar-pct { font-size: 0.75rem; color: var(--muted); }
.prob-slider {
  -webkit-appearance: none; appearance: none; width: 100%; height: 6px; border-radius: 999px;
  background: linear-gradient(90deg, var(--accent) var(--slider-pct, 50%), var(--panel-alt) var(--slider-pct, 50%));
  outline: none; cursor: pointer; margin-bottom: 6px;
}
.prob-slider::-webkit-slider-thumb {
  -webkit-appearance: none; appearance: none; width: 20px; height: 20px;
  border-radius: 50%; background: var(--accent); border: 3px solid var(--panel);
  box-shadow: 0 2px 8px rgba(0,0,0,0.25); cursor: grab;
}
.prob-slider::-moz-range-thumb {
  width: 20px; height: 20px; border-radius: 50%; background: var(--accent);
  border: 3px solid var(--panel); box-shadow: 0 2px 8px rgba(0,0,0,0.25); cursor: grab;
}
.prob-slider-caption { font-size: 0.82rem; color: var(--muted); text-align: center; line-height: 1.5; margin-top: 4px; }

/* Gate reference cards */
.gate-ref-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(145px, 1fr)); gap: 10px; margin: 20px 0; }
.gate-ref-card {
  border: 2px solid var(--gate-ref-color, var(--border));
  border-radius: 12px; padding: 12px; background: var(--panel);
  cursor: pointer; transition: transform 120ms ease, box-shadow 140ms ease;
}
.gate-ref-card:hover { transform: translateY(-2px); box-shadow: 0 0 0 1px var(--gate-ref-color, var(--border)), 0 8px 20px rgba(0,0,0,0.12); }
.gate-ref-symbol { font-size: 1.4rem; font-weight: 700; font-family: "IBM Plex Mono", monospace; color: var(--gate-ref-color, var(--text)); margin-bottom: 5px; }
.gate-ref-name { font-size: 0.78rem; font-weight: 700; color: var(--text); margin-bottom: 3px; }
.gate-ref-desc { font-size: 0.75rem; color: var(--muted); line-height: 1.45; }
.gate-ref-detail { display: none; font-size: 0.8rem; color: var(--text); margin-top: 8px; padding-top: 8px; border-top: 1px solid var(--border); line-height: 1.55; }
.gate-ref-card.expanded .gate-ref-detail { display: block; }

/* Exponential growth chart */
.exp-growth-wrap { background: var(--panel); border: 1px solid var(--border); border-radius: 14px; padding: 20px; margin: 24px 0; }
.exp-growth-label { font-size: 0.72rem; font-weight: 700; letter-spacing: 0.05em; text-transform: uppercase; color: var(--accent-2); margin-bottom: 14px; display: flex; align-items: center; gap: 6px; }
.exp-growth-chart { display: flex; align-items: flex-end; gap: 5px; height: 120px; margin-bottom: 10px; }
.exp-bar {
  flex: 1; border-radius: 6px 6px 0 0; min-height: 4px;
  position: relative; cursor: pointer; transition: filter 120ms ease;
}
.exp-bar:hover { filter: brightness(1.18); }
.exp-bar-tooltip {
  position: absolute; bottom: 100%; left: 50%; transform: translateX(-50%) translateY(-4px);
  background: var(--panel-alt); border: 1px solid var(--border); border-radius: 8px;
  padding: 4px 8px; font-size: 0.72rem; font-family: "IBM Plex Mono", monospace;
  white-space: nowrap; pointer-events: none; opacity: 0; transition: opacity 120ms ease; z-index: 10;
}
.exp-bar:hover .exp-bar-tooltip { opacity: 1; }
.exp-axis-labels { display: flex; gap: 5px; font-size: 0.72rem; font-family: "IBM Plex Mono", monospace; color: var(--muted); }
.exp-axis-labels span { flex: 1; text-align: center; }
.exp-caption { font-size: 0.82rem; color: var(--muted); line-height: 1.5; margin-top: 8px; text-align: center; }

@media (max-width: 640px) {
  .lesson-compare-grid { grid-template-columns: 1fr; }
  .gate-ref-grid { grid-template-columns: repeat(auto-fill, minmax(120px, 1fr)); }
}