/* ── Reset & Base ─────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg: #0c0c0f;
  --bg2: #13131a;
  --bg3: #1a1a24;
  --bg4: #22222f;
  --border: rgba(255,255,255,0.07);
  --border2: rgba(255,255,255,0.12);
  --text: #e8e6f0;
  --text2: #9390a8;
  --text3: #5e5c73;
  --accent: #a78bfa;
  --accent2: #7c3aed;
  --accent-dim: rgba(167,139,250,0.1);
  --teal: #34d399;
  --teal-dim: rgba(52,211,153,0.1);
  --coral: #fb923c;
  --coral-dim: rgba(251,146,60,0.1);
  --blue: #60a5fa;
  --blue-dim: rgba(96,165,250,0.1);
  --red: #f87171;
  --sidebar-w: 280px;
  --font-body: 'DM Sans', sans-serif;
  --font-display: 'Fraunces', serif;
  --font-mono: 'DM Mono', monospace;
  --radius: 10px;
  --radius-lg: 16px;
}

/* ── Light theme ──────────────────────────────────────── */
body.light {
  --bg: #f8f7f4;
  --bg2: #ffffff;
  --bg3: #f1efe9;
  --bg4: #e8e5dc;
  --border: rgba(0,0,0,0.07);
  --border2: rgba(0,0,0,0.13);
  --text: #1a1825;
  --text2: #4a4760;
  --text3: #9390a8;
  --accent: #6d28d9;
  --accent2: #5b21b6;
  --accent-dim: rgba(109,40,217,0.08);
  --teal: #0d7a56;
  --teal-dim: rgba(13,122,86,0.08);
  --coral: #c2410c;
  --coral-dim: rgba(194,65,12,0.08);
  --blue: #1d4ed8;
  --blue-dim: rgba(29,78,216,0.08);
  --red: #dc2626;
}

body.light .kw  { color: #6d28d9; }
body.light .ty  { color: #0d7a56; }
body.light .cm  { color: #9390a8; }
body.light .st  { color: #c2410c; }
body.light .fn  { color: #1d4ed8; }
body.light .num { color: #c2410c; }
body.light pre  { background: #f1efe9; }

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-body);
  background: var(--bg);
  color: var(--text);
  display: flex;
  min-height: 100vh;
  line-height: 1.7;
}

/* ── Sidebar ──────────────────────────────────────── */
.sidebar {
  width: var(--sidebar-w);
  min-height: 100vh;
  background: var(--bg2);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  position: fixed;
  top: 0; left: 0;
  z-index: 100;
  transition: transform .3s cubic-bezier(.4,0,.2,1);
}

.sidebar-header {
  padding: 2rem 1.5rem 1.25rem;
  border-bottom: 1px solid var(--border);
}

.logo {
  font-family: var(--font-display);
  font-size: 1.6rem;
  font-weight: 600;
  color: var(--text);
  letter-spacing: -0.02em;
}

.logo-accent { color: var(--accent); }

.sidebar-sub {
  font-size: 11px;
  color: var(--text3);
  margin-top: 4px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.sidebar-nav {
  flex: 1;
  overflow-y: auto;
  padding: 1rem 0;
}

.sidebar-nav::-webkit-scrollbar { width: 3px; }
.sidebar-nav::-webkit-scrollbar-track { background: transparent; }
.sidebar-nav::-webkit-scrollbar-thumb { background: var(--border2); border-radius: 2px; }

.nav-section-label {
  font-size: 10px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text3);
  padding: 1rem 1.5rem 0.4rem;
  font-weight: 500;
}

.nav-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 0.55rem 1.5rem;
  cursor: pointer;
  font-size: 13.5px;
  color: var(--text2);
  transition: all .15s;
  border-left: 2px solid transparent;
  user-select: none;
}

.nav-item:hover { color: var(--text); background: rgba(255,255,255,0.03); }

.nav-item.active {
  color: var(--accent);
  border-left-color: var(--accent);
  background: var(--accent-dim);
}

.nav-item.done .nav-dot { background: var(--teal); }

.nav-dot {
  width: 6px; height: 6px;
  border-radius: 50%;
  background: var(--border2);
  flex-shrink: 0;
  transition: background .2s;
}

.nav-item.active .nav-dot { background: var(--accent); }

.nav-num {
  font-family: var(--font-mono);
  font-size: 10px;
  color: var(--text3);
  min-width: 16px;
}

.sidebar-footer {
  padding: 1.25rem 1.5rem;
  border-top: 1px solid var(--border);
}

.progress-label {
  font-size: 11px;
  color: var(--text3);
  margin-bottom: 8px;
  letter-spacing: 0.04em;
}

.progress-bar-wrap {
  height: 3px;
  background: var(--bg4);
  border-radius: 2px;
  overflow: hidden;
  margin-bottom: 6px;
}

.progress-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent2), var(--accent));
  border-radius: 2px;
  width: 0%;
  transition: width .4s cubic-bezier(.4,0,.2,1);
}

.progress-text {
  font-size: 11px;
  color: var(--text3);
  font-family: var(--font-mono);
}

/* ── Mobile Header ────────────────────────────────── */
.mobile-header {
  display: none;
  position: fixed;
  top: 0; left: 0; right: 0;
  height: 56px;
  background: var(--bg2);
  border-bottom: 1px solid var(--border);
  align-items: center;
  justify-content: space-between;
  padding: 0 1rem;
  z-index: 200;
}

.hamburger {
  background: none;
  border: none;
  cursor: pointer;
  width: 40px; height: 40px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 5px;
}

.hamburger span {
  display: block;
  width: 20px; height: 1.5px;
  background: var(--text2);
  transition: all .2s;
}

/* ── Main Content ─────────────────────────────────── */
.main {
  margin-left: var(--sidebar-w);
  flex: 1;
  min-height: 100vh;
}

.content-wrap {
  max-width: 780px;
  margin: 0 auto;
  padding: 3rem 2.5rem 6rem;
}

/* ── Topic Page ───────────────────────────────────── */
.topic-page { display: none; }
.topic-page.active { display: block; animation: fadeUp .3s ease; }

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(12px); }
  to   { opacity: 1; transform: translateY(0); }
}

.topic-eyebrow {
  font-size: 11px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 500;
  margin-bottom: .6rem;
  font-family: var(--font-mono);
}

.topic-title {
  font-family: var(--font-display);
  font-size: 2.4rem;
  font-weight: 600;
  line-height: 1.15;
  letter-spacing: -0.03em;
  color: var(--text);
  margin-bottom: 1rem;
}

.topic-intro {
  font-size: 16px;
  color: var(--text2);
  line-height: 1.75;
  margin-bottom: 2.5rem;
  padding-bottom: 2rem;
  border-bottom: 1px solid var(--border);
}

/* ── Cards ────────────────────────────────────────── */
.card {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  margin-bottom: 1.25rem;
  transition: border-color .2s;
}

.card:hover { border-color: var(--border2); }

.card-label {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-size: 10px;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 3px 10px;
  border-radius: 20px;
  margin-bottom: 10px;
}

.label-tip   { background: var(--teal-dim);  color: var(--teal); }
.label-core  { background: var(--accent-dim); color: var(--accent); }
.label-next  { background: var(--blue-dim);  color: var(--blue); }
.label-warn  { background: var(--coral-dim); color: var(--coral); }

.card h3 {
  font-size: 16px;
  font-weight: 500;
  color: var(--text);
  margin-bottom: .6rem;
  letter-spacing: -0.01em;
}

.card p {
  font-size: 14.5px;
  color: var(--text2);
  line-height: 1.7;
  margin-bottom: .75rem;
}

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

/* ── Code Blocks ──────────────────────────────────── */
pre {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.75;
  overflow-x: auto;
  margin: .9rem 0;
  position: relative;
}

pre::-webkit-scrollbar { height: 3px; }
pre::-webkit-scrollbar-track { background: transparent; }
pre::-webkit-scrollbar-thumb { background: var(--border2); }

code { font-family: var(--font-mono); font-size: 13px; }

.kw  { color: #c084fc; }
.ty  { color: var(--teal); }
.cm  { color: var(--text3); font-style: italic; }
.st  { color: var(--coral); }
.fn  { color: var(--blue); }
.num { color: #fb923c; }

/* inline code */
p code, li code {
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1px 6px;
  font-size: 12.5px;
  color: var(--accent);
}

/* ── Insight Box ──────────────────────────────────── */
.insight {
  border-left: 3px solid var(--accent);
  background: var(--accent-dim);
  border-radius: 0 var(--radius) var(--radius) 0;
  padding: .9rem 1.1rem;
  margin: 1rem 0;
  font-size: 13.5px;
  color: var(--text2);
  line-height: 1.65;
}

.insight strong { color: var(--accent); font-weight: 500; }

.insight-teal {
  border-left-color: var(--teal);
  background: var(--teal-dim);
}
.insight-teal strong { color: var(--teal); }

.insight-coral {
  border-left-color: var(--coral);
  background: var(--coral-dim);
}
.insight-coral strong { color: var(--coral); }

/* ── Comparison Grid ──────────────────────────────── */
.compare-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: .75rem;
  margin: 1rem 0;
}

.compare-col {
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1rem;
}

.compare-col h4 {
  font-size: 11px;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: .6rem;
}

.compare-col.bad  h4 { color: var(--red); }
.compare-col.good h4 { color: var(--teal); }
.compare-col.bad  { border-color: rgba(248,113,113,0.2); }
.compare-col.good { border-color: rgba(52,211,153,0.2); }

/* ── Quiz ─────────────────────────────────────────── */
.quiz-box {
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
  margin-top: 1rem;
}

.quiz-q {
  font-size: 14px;
  font-weight: 500;
  color: var(--text);
  margin-bottom: .9rem;
}

.quiz-opts { display: flex; flex-direction: column; gap: 8px; }

.quiz-opt {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: .65rem 1rem;
  font-size: 13.5px;
  color: var(--text2);
  cursor: pointer;
  text-align: left;
  font-family: var(--font-body);
  transition: all .15s;
}

.quiz-opt:hover { border-color: var(--border2); color: var(--text); }
.quiz-opt.correct { border-color: var(--teal); background: var(--teal-dim); color: var(--teal); }
.quiz-opt.wrong   { border-color: var(--red);  background: rgba(248,113,113,0.08); color: var(--red); }
.quiz-opt:disabled { cursor: default; }

.quiz-fb {
  margin-top: .75rem;
  font-size: 13px;
  color: var(--text2);
  line-height: 1.6;
  display: none;
  padding: .65rem .9rem;
  border-radius: 6px;
  background: var(--bg4);
}

/* ── Navigation Buttons ───────────────────────────── */
.topic-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 3rem;
  padding-top: 2rem;
  border-top: 1px solid var(--border);
  gap: 1rem;
}

.nav-btn {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: .7rem 1.3rem;
  border-radius: var(--radius);
  font-size: 13.5px;
  font-family: var(--font-body);
  cursor: pointer;
  transition: all .15s;
  text-decoration: none;
}

.nav-btn-prev {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text2);
}

.nav-btn-prev:hover { border-color: var(--border2); color: var(--text); }

.nav-btn-next {
  background: var(--accent2);
  border: 1px solid transparent;
  color: #fff;
  margin-left: auto;
}

.nav-btn-next:hover { background: var(--accent); }

.nav-btn-finish {
  background: var(--teal);
  border: 1px solid transparent;
  color: var(--bg);
  font-weight: 500;
  margin-left: auto;
}

.nav-btn-finish:hover { opacity: .9; }

/* ── Mental Model Box ─────────────────────────────── */
.mental-model {
  background: linear-gradient(135deg, var(--bg3), var(--bg2));
  border: 1px solid var(--accent2);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  margin: 1.5rem 0;
}

.mental-model h4 {
  font-family: var(--font-display);
  font-size: 1rem;
  font-weight: 600;
  color: var(--accent);
  margin-bottom: .75rem;
  font-style: italic;
}

.mental-model p {
  font-size: 14px;
  color: var(--text2);
  line-height: 1.7;
}

/* ── Pill Tags ────────────────────────────────────── */
.tag-row { display: flex; flex-wrap: wrap; gap: 8px; margin: .75rem 0; }

.tag {
  font-size: 11px;
  padding: 3px 10px;
  border-radius: 20px;
  font-family: var(--font-mono);
  border: 1px solid;
}

.tag-purple { background: var(--accent-dim); color: var(--accent); border-color: rgba(167,139,250,0.3); }
.tag-teal   { background: var(--teal-dim);   color: var(--teal);   border-color: rgba(52,211,153,0.3); }
.tag-coral  { background: var(--coral-dim);  color: var(--coral);  border-color: rgba(251,146,60,0.3); }
.tag-blue   { background: var(--blue-dim);   color: var(--blue);   border-color: rgba(96,165,250,0.3); }

/* ── Hero / Welcome ───────────────────────────────── */
.hero {
  padding: 1rem 0 3rem;
}

.hero-eyebrow {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 1.25rem;
}

.hero-title {
  font-family: var(--font-display);
  font-size: 3.2rem;
  font-weight: 600;
  line-height: 1.1;
  letter-spacing: -0.04em;
  margin-bottom: 1.25rem;
}

.hero-title em {
  font-style: italic;
  color: var(--accent);
}

.hero-body {
  font-size: 16px;
  color: var(--text2);
  line-height: 1.75;
  max-width: 560px;
  margin-bottom: 2rem;
}

.path-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: .75rem;
  margin: 2rem 0;
}

.path-card {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.1rem 1.25rem;
  cursor: pointer;
  transition: all .2s;
}

.path-card:hover {
  border-color: var(--accent);
  background: var(--accent-dim);
  transform: translateY(-2px);
}

.path-num {
  font-family: var(--font-mono);
  font-size: 10px;
  color: var(--text3);
  margin-bottom: 6px;
}

.path-card h3 {
  font-size: 14px;
  font-weight: 500;
  color: var(--text);
  margin-bottom: 4px;
}

.path-card p {
  font-size: 12px;
  color: var(--text3);
  line-height: 1.5;
}

.start-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--accent2);
  color: #fff;
  border: none;
  padding: .85rem 1.75rem;
  border-radius: var(--radius);
  font-size: 15px;
  font-family: var(--font-body);
  cursor: pointer;
  transition: all .2s;
  font-weight: 500;
}

.start-btn:hover { background: var(--accent); transform: translateY(-1px); }

/* ── Completion Screen ────────────────────────────── */
.completion {
  text-align: center;
  padding: 4rem 2rem;
}

.completion-icon {
  font-size: 4rem;
  margin-bottom: 1.5rem;
  display: block;
}

.completion h2 {
  font-family: var(--font-display);
  font-size: 2.5rem;
  font-weight: 600;
  letter-spacing: -0.03em;
  margin-bottom: 1rem;
  color: var(--teal);
}

.completion p {
  font-size: 16px;
  color: var(--text2);
  max-width: 480px;
  margin: 0 auto 2rem;
  line-height: 1.7;
}

/* ── Theme Toggle ─────────────────────────────────────── */
.theme-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 0;
}

.theme-toggle {
  display: flex;
  align-items: center;
  gap: 6px;
  background: var(--bg3);
  border: 1px solid var(--border2);
  border-radius: 20px;
  padding: 4px 12px 4px 8px;
  cursor: pointer;
  font-size: 12px;
  color: var(--text2);
  font-family: var(--font-body);
  transition: all .2s;
}

.theme-toggle:hover { background: var(--bg4); color: var(--text); }
.theme-icon { font-size: 13px; line-height: 1; }

.theme-toggle-mobile {
  background: none;
  border: 1px solid var(--border2);
  border-radius: 8px;
  width: 36px; height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  font-size: 15px;
  color: var(--text2);
  transition: all .2s;
}

.theme-toggle-mobile:hover { background: var(--bg3); color: var(--text); }

/* ── Overlay ──────────────────────────────────────── */
.overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.6);
  z-index: 99;
}

.overlay.visible { display: block; }

/* ── Responsive ───────────────────────────────────── */
@media (max-width: 768px) {
  .mobile-header { display: flex; }
  .sidebar {
    transform: translateX(-100%);
    top: 0;
  }
  .sidebar.open { transform: translateX(0); }
  .main { margin-left: 0; padding-top: 56px; }
  .content-wrap { padding: 2rem 1.25rem 5rem; }
  .hero-title { font-size: 2.2rem; }
  .topic-title { font-size: 1.9rem; }
  .compare-grid { grid-template-columns: 1fr; }
}