:root {
  --course-bg: #f6f8fb;
  --course-surface: #ffffff;
  --course-text: #172033;
  --course-muted: #64748b;
  --course-primary: #3457d5;
  --course-primary-strong: #233ba4;
  --course-accent: #21a179;
  --course-border: #dbe3ee;
  --course-warning: #b86b00;
  --course-code: #111827;
  --course-radius: 1rem;
  --course-shadow: 0 12px 32px rgba(15, 23, 42, .08);
}
[data-theme="dark"] {
  --course-bg: #0f172a;
  --course-surface: #172033;
  --course-text: #e5edf7;
  --course-muted: #a5b4c7;
  --course-primary: #89a5ff;
  --course-primary-strong: #b4c5ff;
  --course-accent: #63d6ad;
  --course-border: #334155;
  --course-code: #020617;
  --course-shadow: 0 12px 32px rgba(0, 0, 0, .25);
}
html { scroll-behavior: smooth; }
body {
  background: var(--course-bg);
  color: var(--course-text);
  font-family: Inter, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}
a { color: var(--course-primary); }
.course-navbar {
  background: color-mix(in srgb, var(--course-surface) 92%, transparent);
  border-bottom: 1px solid var(--course-border);
  backdrop-filter: blur(12px);
}
.hero {
  padding: 5rem 0 3rem;
}
.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: .5rem;
  padding: .5rem .75rem;
  border-radius: 999px;
  color: var(--course-primary-strong);
  background: color-mix(in srgb, var(--course-primary) 12%, transparent);
  font-weight: 700;
}
.course-card, .lesson-card, .focus-panel {
  background: var(--course-surface);
  border: 1px solid var(--course-border);
  border-radius: var(--course-radius);
  box-shadow: var(--course-shadow);
}
.course-card {
  height: 100%;
  padding: 1.25rem;
  transition: transform .2s ease, border-color .2s ease;
}
.course-card:hover {
  transform: translateY(-3px);
  border-color: var(--course-primary);
}
.level-number {
  width: 2.5rem;
  height: 2.5rem;
  display: inline-grid;
  place-items: center;
  border-radius: .75rem;
  background: color-mix(in srgb, var(--course-primary) 14%, transparent);
  color: var(--course-primary-strong);
  font-weight: 800;
}
.text-muted-custom { color: var(--course-muted); }
.progress {
  background: color-mix(in srgb, var(--course-border) 50%, transparent);
}
.progress-bar { background: var(--course-accent); }
.btn-primary {
  background: var(--course-primary);
  border-color: var(--course-primary);
}
.btn-primary:hover {
  background: var(--course-primary-strong);
  border-color: var(--course-primary-strong);
}
.btn-outline-primary {
  color: var(--course-primary);
  border-color: var(--course-primary);
}
.lesson-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 18rem;
  gap: 1.5rem;
}
.lesson-card { padding: 1.5rem; margin-bottom: 1.25rem; }
.lesson-sidebar {
  position: sticky;
  top: 5.5rem;
  align-self: start;
}
.lesson-step {
  border-left: 4px solid var(--course-border);
  padding-left: 1rem;
}
.lesson-step.is-complete { border-left-color: var(--course-accent); }
.checklist-item {
  display: flex;
  gap: .75rem;
  align-items: flex-start;
  padding: .75rem 0;
  border-bottom: 1px solid var(--course-border);
}
.checklist-item:last-child { border-bottom: 0; }
.code-editor {
  width: 100%;
  min-height: 220px;
  resize: vertical;
  border: 0;
  border-radius: .75rem;
  padding: 1rem;
  background: var(--course-code);
  color: #e5edf7;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  line-height: 1.55;
}
.output-panel {
  min-height: 90px;
  white-space: pre-wrap;
  background: color-mix(in srgb, var(--course-code) 92%, white 8%);
  color: #e5edf7;
  border-radius: .75rem;
  padding: 1rem;
}
.focus-mode .optional-content,
.focus-mode .lesson-sidebar,
.focus-mode .course-navbar .secondary-action {
  display: none !important;
}
.focus-mode .lesson-layout { grid-template-columns: minmax(0, 760px); justify-content: center; }

.tag {
  display: inline-block;
  padding: .25rem .55rem;
  border-radius: 999px;
  font-size: .78rem;
  font-weight: 700;
  background: color-mix(in srgb, var(--course-primary) 12%, transparent);
  color: var(--course-primary-strong);
}
.status-planned { color: var(--course-muted); }
.status-active { color: var(--course-accent); font-weight: 700; }
kbd {
  background: var(--course-code);
  color: white;
  border-radius: .35rem;
  padding: .15rem .4rem;
}
@media (max-width: 991.98px) {
  .lesson-layout { grid-template-columns: 1fr; }
  .lesson-sidebar { position: static; }
  .hero { padding-top: 3rem; }
}
/* v1.0 integrated course components */
body { min-height: 100vh; }
.course-navbar .navbar-brand { color: var(--course-text); }
.course-navbar .nav-link { color: var(--course-muted); }
.course-navbar .nav-link:hover { color: var(--course-primary); }
.course-shell { width: min(1180px, calc(100% - 2rem)); margin-inline: auto; }
.course-stats { display: grid; grid-template-columns: repeat(3, 1fr); gap: .75rem; }
.stat-card { padding: 1rem; border: 1px solid var(--course-border); border-radius: .85rem; background: var(--course-surface); }
.stat-card strong { display: block; font-size: 1.55rem; }
.level-card-status { font-size: .8rem; color: var(--course-muted); }
.level-card-status.is-complete { color: var(--course-accent); font-weight: 700; }
.lesson-card { scroll-margin-top: 6rem; }
.lesson-card > h2:first-child { margin-bottom: 1rem; }
.lesson-card pre,
.code-block {
  overflow: auto;
  background: var(--course-code);
  color: #e5edf7;
  padding: 1rem;
  border-radius: .75rem;
  line-height: 1.55;
  white-space: pre;
}
.lesson-card pre code { color: inherit; }
.lesson-card code:not(pre code) { color: var(--course-primary-strong); background: color-mix(in srgb, var(--course-primary) 10%, transparent); padding: .08rem .28rem; border-radius: .3rem; }
.lesson-card .alert code { color: inherit; background: transparent; padding: 0; }
.lesson-meta { display: flex; flex-wrap: wrap; gap: .5rem; }
.lesson-actions { display: flex; flex-wrap: wrap; gap: .65rem; margin-top: 1rem; }
.lesson-navigation { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; margin-block: 1.5rem 3rem; }
.lesson-navigation .next { text-align: right; }
.sidebar-nav a { display: block; padding: .35rem 0; text-decoration: none; }
.callout { border-left: 4px solid var(--course-accent); padding: .85rem 1rem; border-radius: 0 .75rem .75rem 0; background: color-mix(in srgb, var(--course-accent) 10%, var(--course-surface)); }
.filters-toolbar { display: flex; flex-wrap: wrap; gap: .75rem; align-items: center; }
.filters-toolbar input, .filters-toolbar select { background: var(--course-surface); color: var(--course-text); border: 1px solid var(--course-border); border-radius: .65rem; padding: .65rem .8rem; }
.lesson-list-card { background: var(--course-surface); border: 1px solid var(--course-border); border-radius: .9rem; padding: 1rem; height: 100%; }
.lesson-list-card.is-complete { border-color: var(--course-accent); }
.lesson-list-card.is-complete .completion-label { color: var(--course-accent); font-weight: 700; }
.project-card[hidden], .lesson-list-card[hidden] { display: none !important; }
.copy-feedback { min-width: 7rem; }
.focus-mode .focus-hide { display: none !important; }
.focus-mode .lesson-layout { grid-template-columns: minmax(0, 780px); }
.focus-mode .lesson-card { opacity: 1; }
[data-theme="dark"] .alert-success { color: #c7f9e7; background: #143c31; border-color: #23614e; }
[data-theme="dark"] .alert-warning { color: #ffe7bd; background: #4a3211; border-color: #76531b; }
[data-theme="dark"] .alert-primary { color: #dce5ff; background: #1f3068; border-color: #3855a4; }
@media (max-width: 767.98px) {
  .course-stats { grid-template-columns: 1fr; }
  .lesson-navigation { grid-template-columns: 1fr; }
  .lesson-navigation .next { text-align: left; }
}


/* v2.1 beginner environment preparation */
.beginner-intro {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 1rem;
  align-items: start;
  padding: 1rem;
  border: 1px solid var(--course-border);
  border-radius: .85rem;
  background: color-mix(in srgb, var(--course-primary) 7%, var(--course-surface));
}
.beginner-intro__number {
  width: 2.35rem;
  height: 2.35rem;
  display: grid;
  place-items: center;
  border-radius: 50%;
  background: var(--course-primary);
  color: white;
  font-weight: 800;
}
.setup-step {
  border: 1px solid var(--course-border);
  border-radius: .9rem;
  padding: 1.15rem;
  margin-bottom: 1rem;
  background: var(--course-surface);
}
.setup-step__header { display: flex; gap: .8rem; align-items: flex-start; }
.setup-step__number {
  flex: 0 0 2rem;
  width: 2rem;
  height: 2rem;
  display: grid;
  place-items: center;
  border-radius: .55rem;
  background: color-mix(in srgb, var(--course-primary) 18%, transparent);
  color: var(--course-primary-strong);
  font-weight: 800;
}
.expected-result,
.stop-check,
.beginner-warning {
  margin-top: .8rem;
  padding: .8rem 1rem;
  border-radius: .7rem;
}
.expected-result {
  border-left: 4px solid var(--course-accent);
  background: color-mix(in srgb, var(--course-accent) 9%, var(--course-surface));
}
.stop-check {
  border-left: 4px solid var(--course-warning);
  background: color-mix(in srgb, #f59e0b 10%, var(--course-surface));
}
.beginner-warning {
  border: 1px solid color-mix(in srgb, #f59e0b 45%, var(--course-border));
  background: color-mix(in srgb, #f59e0b 8%, var(--course-surface));
}
.command-context {
  display: flex;
  flex-wrap: wrap;
  gap: .5rem;
  margin-bottom: .65rem;
}
.challenge-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1rem;
}
.challenge-card {
  border: 1px solid var(--course-border);
  border-radius: .85rem;
  padding: 1rem;
  background: var(--course-surface);
}
.challenge-card h3 { font-size: 1.05rem; }
.challenge-card--essential { border-top: 4px solid #22c55e; }
.challenge-card--practice { border-top: 4px solid #f59e0b; }
.challenge-card--advanced { border-top: 4px solid #ef4444; }
.checklist-group {
  border: 1px solid var(--course-border);
  border-radius: .85rem;
  padding: 1rem;
  margin-bottom: 1rem;
}
.checklist-group h3 { font-size: 1rem; margin-bottom: .4rem; }
.checklist-help { color: var(--course-muted); font-size: .9rem; }
.troubleshooting-table { width: 100%; border-collapse: collapse; }
.troubleshooting-table th,
.troubleshooting-table td { border-bottom: 1px solid var(--course-border); padding: .8rem; vertical-align: top; }
.troubleshooting-table th { text-align: left; }
@media (max-width: 767.98px) {
  .challenge-grid { grid-template-columns: 1fr; }
  .beginner-intro { grid-template-columns: 1fr; }
}
/* v2.4 expanded conceptual foundations */
.foundation-terms{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:1rem;margin:1.25rem 0}.foundation-term{padding:1rem;border:1px solid var(--color-border,rgba(255,255,255,.1));border-radius:1rem;background:rgba(255,255,255,.035)}.foundation-term h3{font-size:1rem;color:var(--color-cyan,#0ff)}.foundation-term p{margin-bottom:.65rem}.foundation-example{margin-top:1.25rem;padding:1.25rem;border:1px solid rgba(0,255,255,.24);border-radius:1rem;background:rgba(0,255,255,.045)}.reverse-readiness{border-left:4px solid var(--color-cyan,#0ff)}@media(max-width:767.98px){.foundation-terms{grid-template-columns:1fr}}