/* ============================================
   NEXT → NUXT MIGRATION GUIDE — STYLES
   ============================================ */

/* === DESIGN TOKENS === */
:root {
  --font-display: 'Syne', sans-serif;
  --font-body: 'DM Sans', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  /* Light theme */
  --bg-primary: #f7f7f5;
  --bg-secondary: #ffffff;
  --bg-tertiary: #efefec;
  --bg-code: #1a1a2e;
  --bg-sidebar: #ffffff;
  --bg-card: #ffffff;
  --bg-hover: #f0f0ed;

  --text-primary: #0f0f0f;
  --text-secondary: #555550;
  --text-muted: #999990;
  --text-code: #e8e8f0;
  --text-inverse: #ffffff;

  --border: #e5e5e0;
  --border-strong: #c8c8c0;

  --accent-next: #000000;
  --accent-nuxt: #00dc82;
  --accent-nuxt-dim: #00dc8222;
  --accent-warning: #f59e0b;
  --accent-danger: #ef4444;
  --accent-info: #3b82f6;
  --accent-success: #10b981;

  --shadow-sm: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
  --shadow-md: 0 4px 16px rgba(0,0,0,0.08), 0 2px 4px rgba(0,0,0,0.04);
  --shadow-lg: 0 16px 40px rgba(0,0,0,0.12);

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;

  --sidebar-w: 260px;
  --topbar-h: 58px;
  --transition: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="dark"] {
  --bg-primary: #0c0c0e;
  --bg-secondary: #111116;
  --bg-tertiary: #18181f;
  --bg-code: #0a0a12;
  --bg-sidebar: #111116;
  --bg-card: #18181f;
  --bg-hover: #1e1e28;

  --text-primary: #f0f0f5;
  --text-secondary: #9999aa;
  --text-muted: #55556a;
  --text-code: #dde8ff;
  --text-inverse: #0c0c0e;

  --border: #22222e;
  --border-strong: #33334a;

  --accent-next: #ffffff;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 16px rgba(0,0,0,0.4);
  --shadow-lg: 0 16px 40px rgba(0,0,0,0.6);
}

/* === RESET & BASE === */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
  font-family: var(--font-body);
  background: var(--bg-primary);
  color: var(--text-primary);
  font-size: 15px;
  line-height: 1.7;
  overflow-x: hidden;
  transition: background var(--transition), color var(--transition);
}

/* === TOPBAR === */
.topbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--topbar-h);
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 20px;
  z-index: 100;
  backdrop-filter: blur(12px);
  transition: background var(--transition), border-color var(--transition);
}

.topbar-left, .topbar-right { display: flex; align-items: center; gap: 16px; }

.menu-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}
.menu-toggle span {
  display: block; width: 22px; height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: var(--transition);
}

.brand {
  display: flex;
  align-items: center;
  gap: 6px;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 15px;
  letter-spacing: -0.02em;
}
.brand-next { color: var(--accent-next); }
.brand-arrow { color: var(--text-muted); font-size: 13px; }
.brand-nuxt { color: var(--accent-nuxt); }
.brand-label {
  color: var(--text-muted);
  font-weight: 400;
  font-family: var(--font-body);
  font-size: 12px;
  margin-left: 4px;
  display: none;
}
@media (min-width: 768px) { .brand-label { display: inline; } }

/* Progress pill */
.progress-pill {
  position: relative;
  height: 28px;
  width: 160px;
  background: var(--bg-tertiary);
  border-radius: 20px;
  overflow: hidden;
  border: 1px solid var(--border);
  cursor: default;
}
.progress-pill-bar {
  position: absolute;
  top: 0; left: 0; bottom: 0;
  width: 0%;
  background: linear-gradient(90deg, var(--accent-nuxt), #00b86a);
  border-radius: 20px;
  transition: width 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}
.progress-pill-text {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  height: 100%;
  font-size: 11px;
  font-weight: 600;
  font-family: var(--font-mono);
  color: var(--text-primary);
  z-index: 1;
}

.theme-toggle {
  width: 36px; height: 36px;
  border-radius: 50%;
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-secondary);
  transition: var(--transition);
}
.theme-toggle:hover { background: var(--bg-hover); color: var(--text-primary); }
.theme-toggle svg { width: 16px; height: 16px; }
[data-theme="dark"] .icon-sun { display: block; }
[data-theme="dark"] .icon-moon { display: none; }
[data-theme="light"] .icon-sun { display: none; }
[data-theme="light"] .icon-moon { display: block; }

/* === SIDEBAR === */
.sidebar {
  position: fixed;
  top: var(--topbar-h);
  left: 0;
  bottom: 0;
  width: var(--sidebar-w);
  background: var(--bg-sidebar);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  z-index: 90;
  transition: transform var(--transition), background var(--transition);
}
.sidebar-inner { padding: 20px 0 40px; }

.sidebar-section-label {
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-muted);
  padding: 0 20px 8px;
  margin-top: 8px;
}

.sidebar-nav { display: flex; flex-direction: column; gap: 1px; }

.nav-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 8px 20px;
  cursor: pointer;
  border-radius: 0;
  transition: var(--transition);
  border-left: 3px solid transparent;
  position: relative;
  text-decoration: none;
  color: var(--text-secondary);
  font-size: 13.5px;
}
.nav-item:hover { background: var(--bg-hover); color: var(--text-primary); }
.nav-item.active {
  background: var(--accent-nuxt-dim);
  border-left-color: var(--accent-nuxt);
  color: var(--accent-nuxt);
  font-weight: 600;
}
.nav-item.completed .nav-check { opacity: 1; }
.nav-check {
  margin-left: auto;
  width: 16px; height: 16px;
  border-radius: 50%;
  background: var(--accent-nuxt);
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  transition: opacity 0.3s;
  flex-shrink: 0;
}
.nav-check::after { content: '✓'; font-size: 9px; color: white; font-weight: 700; }
.nav-number {
  width: 20px; height: 20px;
  border-radius: 50%;
  background: var(--bg-tertiary);
  display: flex; align-items: center; justify-content: center;
  font-size: 10px;
  font-family: var(--font-mono);
  color: var(--text-muted);
  flex-shrink: 0;
}
.nav-item.active .nav-number { background: var(--accent-nuxt); color: white; }

.nav-group-label {
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-muted);
  padding: 16px 20px 6px;
}

.sidebar-footer {
  padding: 16px 20px;
  border-top: 1px solid var(--border);
  margin-top: 20px;
}
.sidebar-stats { display: flex; gap: 20px; }
.stat { font-size: 12px; color: var(--text-muted); }
.stat span { font-weight: 700; color: var(--accent-nuxt); font-family: var(--font-mono); }

.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  z-index: 89;
}

/* === MAIN CONTENT === */
.main-content {
  margin-left: var(--sidebar-w);
  padding-top: var(--topbar-h);
  min-height: 100vh;
  transition: margin-left var(--transition);
}
.content-inner {
  max-width: 900px;
  margin: 0 auto;
  padding: 48px 40px 100px;
}

/* === SECTION === */
.section {
  display: none;
  animation: fadeIn 0.35s ease;
}
.section.visible { display: block; }
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

/* === HERO === */
.hero {
  text-align: center;
  padding: 60px 0 40px;
  position: relative;
}
.hero-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent-nuxt);
  margin-bottom: 20px;
  background: var(--accent-nuxt-dim);
  padding: 6px 14px;
  border-radius: 20px;
  border: 1px solid var(--accent-nuxt);
}
.hero-title {
  font-family: var(--font-display);
  font-size: clamp(36px, 6vw, 64px);
  font-weight: 800;
  line-height: 1.05;
  letter-spacing: -0.03em;
  margin-bottom: 20px;
}
.hero-title .hl-next { color: var(--accent-next); }
.hero-title .hl-nuxt { color: var(--accent-nuxt); }
.hero-subtitle {
  font-size: 18px;
  color: var(--text-secondary);
  max-width: 560px;
  margin: 0 auto 40px;
  line-height: 1.6;
}
.hero-stats {
  display: flex;
  justify-content: center;
  gap: 32px;
  flex-wrap: wrap;
}
.hero-stat {
  text-align: center;
  padding: 16px 24px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  min-width: 110px;
}
.hero-stat-num {
  font-family: var(--font-display);
  font-size: 28px;
  font-weight: 800;
  color: var(--accent-nuxt);
  line-height: 1;
  margin-bottom: 4px;
}
.hero-stat-label { font-size: 11px; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.08em; }

/* === SECTION HEADER === */
.section-header {
  margin-bottom: 32px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--border);
}
.section-eyebrow {
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent-nuxt);
  margin-bottom: 8px;
}
.section-title {
  font-family: var(--font-display);
  font-size: clamp(24px, 4vw, 36px);
  font-weight: 800;
  letter-spacing: -0.025em;
  line-height: 1.15;
  margin-bottom: 12px;
}
.section-desc {
  color: var(--text-secondary);
  font-size: 15px;
  line-height: 1.7;
  max-width: 680px;
}

/* === CARDS === */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  margin-bottom: 24px;
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition), border-color var(--transition);
}
.card:hover { box-shadow: var(--shadow-md); }

.card-header {
  padding: 16px 20px;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}
.card-title {
  font-family: var(--font-display);
  font-size: 14px;
  font-weight: 700;
  letter-spacing: -0.01em;
}
.card-body { padding: 20px; }

/* === CODE COMPARISON === */
.code-compare {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  margin-bottom: 24px;
  box-shadow: var(--shadow-sm);
}
.code-pane { display: flex; flex-direction: column; }
.code-pane-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 16px;
  border-bottom: 1px solid var(--border);
  gap: 8px;
}
.code-pane-next .code-pane-header { background: #1a1a1a; border-right: 1px solid var(--border); }
.code-pane-nuxt .code-pane-header { background: #0a1a12; }
.code-pane-label {
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.08em;
  display: flex;
  align-items: center;
  gap: 6px;
}
.label-next { color: #888; }
.label-nuxt { color: var(--accent-nuxt); }
.label-dot { width: 8px; height: 8px; border-radius: 50%; flex-shrink: 0; }
.dot-next { background: #555; }
.dot-nuxt { background: var(--accent-nuxt); }

.code-pane-body {
  background: var(--bg-code);
  flex: 1;
  overflow-x: auto;
}
.code-pane-next .code-pane-body { border-right: 1px solid var(--border); }

pre {
  margin: 0;
  padding: 18px 20px;
  font-family: var(--font-mono);
  font-size: 12.5px;
  line-height: 1.75;
  color: var(--text-code);
  white-space: pre;
  tab-size: 2;
}
code { font-family: var(--font-mono); }

/* Syntax highlight tokens */
.tk-kw { color: #c792ea; }       /* keywords */
.tk-fn { color: #82aaff; }       /* functions */
.tk-str { color: #c3e88d; }      /* strings */
.tk-num { color: #f78c6c; }      /* numbers */
.tk-cmt { color: #546e7a; font-style: italic; }  /* comments */
.tk-tag { color: #ff5572; }      /* JSX/template tags */
.tk-attr { color: #ffcb6b; }     /* attributes */
.tk-type { color: #89ddff; }     /* types */
.tk-var { color: #eeffff; }      /* variables */
.tk-op { color: #89ddff; }       /* operators */
.tk-nuxt { color: #00dc82; }     /* nuxt-specific */
.tk-react { color: #aaaaff; }    /* react-specific */

/* Inline code */
.inline-code {
  font-family: var(--font-mono);
  font-size: 12.5px;
  background: var(--bg-tertiary);
  color: var(--accent-nuxt);
  padding: 2px 6px;
  border-radius: 4px;
  border: 1px solid var(--border);
}

/* === COPY BUTTON === */
.copy-btn {
  background: rgba(255,255,255,0.08);
  border: 1px solid rgba(255,255,255,0.12);
  color: #888;
  border-radius: var(--radius-sm);
  padding: 4px 10px;
  font-size: 11px;
  font-family: var(--font-mono);
  cursor: pointer;
  transition: var(--transition);
  display: flex; align-items: center; gap: 5px;
  flex-shrink: 0;
}
.copy-btn:hover { background: rgba(255,255,255,0.15); color: #ccc; }
.copy-btn.copied { color: var(--accent-nuxt); border-color: var(--accent-nuxt); }

/* === CALLOUT BOXES === */
.callout {
  padding: 14px 18px;
  border-radius: var(--radius-md);
  margin-bottom: 16px;
  display: flex;
  gap: 12px;
  align-items: flex-start;
  font-size: 14px;
  line-height: 1.6;
}
.callout-icon { font-size: 16px; flex-shrink: 0; margin-top: 1px; }
.callout-text { flex: 1; }
.callout-text strong { font-weight: 600; display: block; margin-bottom: 3px; }
.callout-info { background: #1e3a5f22; border: 1px solid #3b82f640; color: #93c5fd; }
.callout-warning { background: #451a0322; border: 1px solid #f59e0b40; color: #fcd34d; }
.callout-danger { background: #450a0a22; border: 1px solid #ef444440; color: #fca5a5; }
.callout-success { background: #052e1622; border: 1px solid #10b98140; color: #6ee7b7; }
.callout-tip { background: #1a1a3a22; border: 1px solid #8b5cf640; color: #c4b5fd; }

[data-theme="light"] .callout-info { background: #eff6ff; border-color: #bfdbfe; color: #1d4ed8; }
[data-theme="light"] .callout-warning { background: #fffbeb; border-color: #fde68a; color: #92400e; }
[data-theme="light"] .callout-danger { background: #fef2f2; border-color: #fecaca; color: #991b1b; }
[data-theme="light"] .callout-success { background: #f0fdf4; border-color: #bbf7d0; color: #166534; }
[data-theme="light"] .callout-tip { background: #f5f3ff; border-color: #ddd6fe; color: #5b21b6; }

/* === EXPAND/COLLAPSE === */
.expander {
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  margin-bottom: 12px;
  overflow: hidden;
}
.expander-trigger {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 18px;
  background: var(--bg-card);
  border: none;
  cursor: pointer;
  text-align: left;
  color: var(--text-primary);
  font-size: 14px;
  font-weight: 500;
  transition: var(--transition);
  gap: 12px;
}
.expander-trigger:hover { background: var(--bg-hover); }
.expander-chevron {
  width: 18px; height: 18px;
  border: 1.5px solid var(--text-muted);
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  flex-shrink: 0;
  transition: transform var(--transition);
  color: var(--text-muted);
  font-size: 10px;
}
.expander.open .expander-chevron { transform: rotate(180deg); }
.expander-body {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}
.expander.open .expander-body { max-height: 2000px; }
.expander-content {
  padding: 4px 18px 18px;
  font-size: 14px;
  line-height: 1.7;
  color: var(--text-secondary);
  border-top: 1px solid var(--border);
}
.expander-content p { margin-bottom: 10px; }
.expander-content p:last-child { margin-bottom: 0; }
.expander-content ul { padding-left: 20px; margin-bottom: 10px; }
.expander-content li { margin-bottom: 6px; }

/* === QUIZ === */
.quiz-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 20px;
  background: linear-gradient(135deg, var(--accent-nuxt), #00b86a);
  color: white;
  border: none;
  border-radius: var(--radius-md);
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  margin-top: 8px;
  box-shadow: 0 4px 12px rgba(0,220,130,0.3);
}
.quiz-btn:hover { transform: translateY(-1px); box-shadow: 0 6px 20px rgba(0,220,130,0.4); }

/* Modal */
.modal-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.7);
  z-index: 200;
  align-items: center;
  justify-content: center;
  padding: 20px;
  backdrop-filter: blur(4px);
}
.modal-overlay.open { display: flex; animation: fadeIn 0.2s ease; }
.modal {
  background: var(--bg-secondary);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-xl);
  width: 100%;
  max-width: 520px;
  box-shadow: var(--shadow-lg);
  overflow: hidden;
  animation: slideUp 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
}
@keyframes slideUp {
  from { opacity: 0; transform: translateY(30px) scale(0.95); }
  to { opacity: 1; transform: translateY(0) scale(1); }
}
.modal-header {
  padding: 20px 24px 16px;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.modal-title { font-family: var(--font-display); font-size: 18px; font-weight: 700; }
.modal-close {
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  color: var(--text-muted);
  width: 28px; height: 28px;
  border-radius: 50%;
  cursor: pointer;
  font-size: 12px;
  display: flex; align-items: center; justify-content: center;
  transition: var(--transition);
}
.modal-close:hover { color: var(--text-primary); }
.modal-body { padding: 20px 24px; }
.modal-footer { padding: 16px 24px; border-top: 1px solid var(--border); display: flex; justify-content: flex-end; gap: 10px; }

/* Quiz options */
.quiz-question { font-size: 15px; font-weight: 500; margin-bottom: 16px; line-height: 1.5; }
.quiz-options { display: flex; flex-direction: column; gap: 8px; margin-bottom: 16px; }
.quiz-option {
  padding: 12px 16px;
  border: 1.5px solid var(--border);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: var(--transition);
  font-size: 14px;
  background: var(--bg-card);
  color: var(--text-primary);
  text-align: left;
  width: 100%;
}
.quiz-option:hover { border-color: var(--accent-nuxt); background: var(--accent-nuxt-dim); }
.quiz-option.selected { border-color: var(--accent-nuxt); background: var(--accent-nuxt-dim); }
.quiz-option.correct { border-color: var(--accent-success); background: #052e1644; color: #6ee7b7; }
.quiz-option.wrong { border-color: var(--accent-danger); background: #450a0a44; color: #fca5a5; }
.quiz-result {
  padding: 12px 16px;
  border-radius: var(--radius-md);
  font-size: 13.5px;
  line-height: 1.5;
  display: none;
}
.quiz-result.show { display: block; }
.quiz-result.pass { background: #052e1644; border: 1px solid var(--accent-success); color: #6ee7b7; }
.quiz-result.fail { background: #450a0a44; border: 1px solid var(--accent-danger); color: #fca5a5; }

/* === TRY IT YOURSELF === */
.try-it {
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  margin-bottom: 24px;
}
.try-it-header {
  padding: 12px 18px;
  background: var(--bg-tertiary);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px;
}
.try-it-title {
  font-size: 13px;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--text-primary);
}
.try-it-icon {
  width: 24px; height: 24px;
  background: linear-gradient(135deg, var(--accent-nuxt), #00b86a);
  border-radius: 6px;
  display: flex; align-items: center; justify-content: center;
  font-size: 12px;
}
.try-it-actions { display: flex; gap: 8px; }
.try-btn {
  padding: 6px 14px;
  border-radius: var(--radius-sm);
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: var(--text-primary);
}
.try-btn:hover { background: var(--bg-hover); }
.try-btn.primary {
  background: var(--accent-nuxt);
  color: #000;
  border-color: var(--accent-nuxt);
}
.try-btn.primary:hover { opacity: 0.85; }

.try-it-editor {
  position: relative;
  background: var(--bg-code);
}
textarea.code-editor {
  width: 100%;
  min-height: 180px;
  padding: 18px 20px;
  font-family: var(--font-mono);
  font-size: 12.5px;
  line-height: 1.75;
  background: transparent;
  color: var(--text-code);
  border: none;
  outline: none;
  resize: vertical;
  tab-size: 2;
}
.try-it-output {
  padding: 14px 18px;
  border-top: 1px solid var(--border);
  background: var(--bg-secondary);
  font-size: 13px;
  min-height: 48px;
}
.output-label {
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-bottom: 6px;
}
.output-content { font-family: var(--font-mono); font-size: 12.5px; color: var(--accent-nuxt); }
.output-error { color: var(--accent-danger); }

/* === MIGRATION CHALLENGE === */
.challenge-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  margin-bottom: 24px;
}
.challenge-pane {
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
}
.challenge-pane-header {
  padding: 12px 16px;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.challenge-pane-title { font-size: 13px; font-weight: 700; font-family: var(--font-mono); }
.challenge-editor {
  background: var(--bg-code);
}
.challenge-editor textarea {
  width: 100%;
  min-height: 280px;
  padding: 16px;
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.7;
  background: transparent;
  color: var(--text-code);
  border: none;
  outline: none;
  resize: vertical;
  tab-size: 2;
}
.challenge-step {
  padding: 14px 18px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border);
  margin-bottom: 12px;
  background: var(--bg-card);
  cursor: pointer;
  transition: var(--transition);
}
.challenge-step:hover { border-color: var(--accent-nuxt); }
.challenge-step.active { border-color: var(--accent-nuxt); background: var(--accent-nuxt-dim); }
.challenge-step.done { border-color: var(--accent-success); }
.challenge-step-num {
  width: 24px; height: 24px;
  border-radius: 50%;
  background: var(--bg-tertiary);
  display: flex; align-items: center; justify-content: center;
  font-size: 11px;
  font-weight: 700;
  font-family: var(--font-mono);
  color: var(--text-muted);
  flex-shrink: 0;
}
.challenge-step.active .challenge-step-num { background: var(--accent-nuxt); color: #000; }
.challenge-step.done .challenge-step-num { background: var(--accent-success); color: white; }
.challenge-step-header { display: flex; align-items: center; gap: 12px; margin-bottom: 4px; }
.challenge-step-title { font-size: 13.5px; font-weight: 600; }
.challenge-step-desc { font-size: 12.5px; color: var(--text-muted); padding-left: 36px; }

/* === BUTTONS === */
.btn {
  padding: 9px 18px;
  border-radius: var(--radius-md);
  font-size: 13.5px;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  border: 1px solid var(--border);
  display: inline-flex;
  align-items: center;
  gap: 8px;
}
.btn-primary {
  background: var(--accent-nuxt);
  color: #000;
  border-color: var(--accent-nuxt);
}
.btn-primary:hover { opacity: 0.85; transform: translateY(-1px); }
.btn-secondary { background: var(--bg-card); color: var(--text-primary); }
.btn-secondary:hover { background: var(--bg-hover); }
.btn-outline {
  background: transparent;
  border-color: var(--accent-nuxt);
  color: var(--accent-nuxt);
}
.btn-outline:hover { background: var(--accent-nuxt-dim); }

/* === NAV CONTROLS === */
.section-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  flex-wrap: wrap;
  gap: 12px;
}
.section-complete-btn {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 20px;
  background: var(--bg-card);
  border: 1.5px solid var(--accent-nuxt);
  color: var(--accent-nuxt);
  border-radius: var(--radius-md);
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
}
.section-complete-btn:hover { background: var(--accent-nuxt-dim); }
.section-complete-btn.done {
  background: var(--accent-nuxt);
  color: #000;
}

/* === TAGS === */
.tag {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 3px 10px;
  border-radius: 20px;
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.04em;
}
.tag-next { background: #1a1a1a; color: #888; border: 1px solid #333; }
.tag-nuxt { background: var(--accent-nuxt-dim); color: var(--accent-nuxt); border: 1px solid var(--accent-nuxt); }
.tag-tip { background: #1a1a3a; color: #a78bfa; border: 1px solid #6d28d9; }
.tag-warn { background: #1a1200; color: #f59e0b; border: 1px solid #b45309; }

/* === DIFF VIEW === */
.diff-line { display: block; padding: 0 4px; border-radius: 3px; }
.diff-add { background: #00dc8218; color: #00dc82; }
.diff-remove { background: #ef444418; color: #fca5a5; text-decoration: line-through; }

/* === COMPARISON TABLE === */
.compare-table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: 24px;
  font-size: 13.5px;
}
.compare-table th, .compare-table td {
  padding: 10px 14px;
  text-align: left;
  border-bottom: 1px solid var(--border);
  vertical-align: top;
}
.compare-table th {
  background: var(--bg-tertiary);
  font-weight: 600;
  font-size: 11px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-muted);
}
.compare-table tr:hover td { background: var(--bg-hover); }
.compare-table .col-concept { color: var(--text-secondary); font-weight: 500; }
.compare-table .col-next { color: #aaa; font-family: var(--font-mono); font-size: 12px; }
.compare-table .col-nuxt { color: var(--accent-nuxt); font-family: var(--font-mono); font-size: 12px; }

/* === FILE TREE === */
.file-tree {
  background: var(--bg-code);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 16px 20px;
  font-family: var(--font-mono);
  font-size: 12.5px;
  line-height: 2;
  margin-bottom: 24px;
  overflow-x: auto;
}
.file-tree-row { display: flex; align-items: center; gap: 8px; white-space: nowrap; }
.file-icon { font-size: 13px; flex-shrink: 0; }
.file-name { color: var(--text-code); }
.file-name.dir { color: #82aaff; }
.file-name.highlight { color: var(--accent-nuxt); font-weight: 600; }
.file-name.muted { color: var(--text-muted); }
.file-comment { color: #546e7a; font-style: italic; font-size: 11px; margin-left: auto; }

/* === TOAST === */
.toast-container { position: fixed; bottom: 24px; right: 24px; z-index: 300; display: flex; flex-direction: column; gap: 8px; }
.toast {
  padding: 12px 18px;
  background: var(--bg-secondary);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-md);
  font-size: 13.5px;
  box-shadow: var(--shadow-lg);
  display: flex;
  align-items: center;
  gap: 10px;
  animation: slideLeft 0.3s ease;
  max-width: 300px;
}
@keyframes slideLeft {
  from { opacity: 0; transform: translateX(30px); }
  to { opacity: 1; transform: translateX(0); }
}
.toast.success { border-color: var(--accent-success); }
.toast.error { border-color: var(--accent-danger); }
.toast-icon { font-size: 16px; }
.toast-msg { color: var(--text-primary); }

/* === MINDSET CARD === */
.mindset-card {
  background: linear-gradient(135deg, #0a1a12, #051210);
  border: 1px solid var(--accent-nuxt);
  border-radius: var(--radius-lg);
  padding: 20px 24px;
  margin-bottom: 24px;
  position: relative;
  overflow: hidden;
}
.mindset-card::before {
  content: '';
  position: absolute;
  top: -40px; right: -40px;
  width: 120px; height: 120px;
  background: radial-gradient(circle, rgba(0,220,130,0.15), transparent);
  border-radius: 50%;
}
[data-theme="light"] .mindset-card {
  background: linear-gradient(135deg, #f0fdf4, #f7fef9);
}
.mindset-title {
  font-family: var(--font-display);
  font-size: 13px;
  font-weight: 700;
  color: var(--accent-nuxt);
  margin-bottom: 10px;
  display: flex;
  align-items: center;
  gap: 8px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}
.mindset-list { list-style: none; padding: 0; }
.mindset-list li {
  font-size: 13.5px;
  color: var(--text-secondary);
  padding: 4px 0;
  display: flex;
  align-items: flex-start;
  gap: 10px;
}
.mindset-list li::before {
  content: '→';
  color: var(--accent-nuxt);
  flex-shrink: 0;
  font-weight: 700;
  margin-top: 1px;
}

/* === PITFALLS === */
.pitfall-list { list-style: none; padding: 0; margin-bottom: 24px; }
.pitfall-item {
  display: flex;
  gap: 12px;
  padding: 14px 16px;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  margin-bottom: 10px;
  background: var(--bg-card);
}
.pitfall-icon { font-size: 18px; flex-shrink: 0; }
.pitfall-title { font-weight: 600; font-size: 13.5px; margin-bottom: 4px; }
.pitfall-desc { font-size: 13px; color: var(--text-secondary); line-height: 1.5; }

/* === RESPONSIVE === */
@media (max-width: 900px) {
  .code-compare { grid-template-columns: 1fr; }
  .code-pane-next .code-pane-body { border-right: none; border-bottom: 1px solid var(--border); }
  .challenge-grid { grid-template-columns: 1fr; }
  .content-inner { padding: 32px 20px 80px; }
}

@media (max-width: 768px) {
  .sidebar {
    transform: translateX(-100%);
    z-index: 95;
  }
  .sidebar.open { transform: translateX(0); }
  .sidebar-overlay.open { display: block; }
  .menu-toggle { display: flex; }
  .main-content { margin-left: 0; }
  .progress-pill { width: 120px; }
  .hero-stats { gap: 12px; }
  .hero-stat { padding: 12px 16px; min-width: 80px; }
  .hero-stat-num { font-size: 22px; }
}

/* === SCROLLBAR === */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border-strong); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--text-muted); }

/* === SELECTION === */
::selection { background: rgba(0,220,130,0.25); color: inherit; }

/* === UTILITY === */
.text-muted { color: var(--text-muted); }
.text-nuxt { color: var(--accent-nuxt); }
.mt-0 { margin-top: 0; }
.mb-0 { margin-bottom: 0; }
.mb-16 { margin-bottom: 16px; }
.mb-24 { margin-bottom: 24px; }
.flex { display: flex; }
.items-center { align-items: center; }
.gap-8 { gap: 8px; }
.gap-12 { gap: 12px; }
.flex-wrap { flex-wrap: wrap; }

.grid-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-bottom: 24px;
}
@media (max-width: 640px) { .grid-2 { grid-template-columns: 1fr; } }

.divider {
  border: none;
  border-top: 1px solid var(--border);
  margin: 32px 0;
}

h4.sub-heading {
  font-family: var(--font-display);
  font-size: 17px;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 12px;
  margin-top: 28px;
  color: var(--text-primary);
}
p.body-text {
  color: var(--text-secondary);
  font-size: 14.5px;
  line-height: 1.75;
  margin-bottom: 14px;
}