*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg: #fff;
  --bg-2: #f8f8f8;
  --text: #111;
  --text-2: #444;
  --text-3: #888;
  --border: #e5e5e5;
  --accent: #2563eb;
  --bad: #dc2626;
  --good: #16a34a;
  --font: system-ui, -apple-system, sans-serif;
  --mono: 'Menlo', 'Monaco', monospace;
}

html { scroll-behavior: smooth; }
body { font-family: var(--font); background: var(--bg); color: var(--text); }

/* Nav */
.site-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  gap: 20px;
  padding: 16px 40px;
  background: rgba(255,255,255,0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.nav-back { font-size: 0.8125rem; color: var(--text-3); text-decoration: none; flex: 1; }
.nav-back:hover { color: var(--text); }
.nav-brand { font-weight: 700; font-size: 0.9rem; }
.nav-code { font-size: 0.8rem; color: var(--text-3); text-decoration: none; }
.nav-code:hover { color: var(--text); }

/* Inner */
.inner {
  max-width: 860px;
  margin: 0 auto;
  padding: 0 40px;
  width: 100%;
}

/* Hero */
.hero {
  border-bottom: 1px solid var(--border);
}
.hero .inner { padding-top: 72px; padding-bottom: 72px; }
.eyebrow {
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-3);
  margin-bottom: 24px;
}
.hero h1 {
  font-size: 3.5rem;
  line-height: 1.07;
  letter-spacing: -0.05em;
  margin-bottom: 20px;
}
.accent { color: var(--accent); }
.sub {
  font-size: 1rem;
  color: var(--text-2);
  line-height: 1.7;
  max-width: 540px;
}

/* Bug sections */
.bug-section {
  border-bottom: 1px solid var(--border);
  padding: 72px 0;
}
.bug-header {
  margin-bottom: 36px;
}
.bug-num {
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-3);
  font-family: var(--mono);
  display: block;
  margin-bottom: 10px;
}
.bug-header h2 {
  font-size: 1.5rem;
  letter-spacing: -0.03em;
  margin-bottom: 10px;
}
.bug-desc {
  font-size: 0.9rem;
  color: var(--text-2);
  line-height: 1.65;
  max-width: 600px;
}
.bug-desc code {
  font-family: var(--mono);
  font-size: 0.85em;
  background: var(--bg-2);
  border: 1px solid var(--border);
  padding: 1px 5px;
  border-radius: 3px;
}

/* Bug layout: stage + diff side by side */
.bug-layout {
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: 24px;
  margin-bottom: 24px;
  align-items: start;
}

/* Demo stage */
.bug-stage {
  display: flex;
  flex-direction: column;
  gap: 16px;
}
.stage-label {
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-3);
}

/* Demo boxes */
.demo-box {
  padding: 20px 24px;
  background: var(--bg-2);
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text);
  text-align: center;
  will-change: transform, opacity;
}
.demo-box.small {
  padding: 14px 20px;
  font-size: 0.85rem;
}
.accent-box { border-color: var(--accent); color: var(--accent); }
.two-boxes { display: flex; flex-direction: column; gap: 8px; }

/* Item list for bug 4 */
.item-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.list-item {
  padding: 12px 16px;
  background: var(--bg-2);
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 0.85rem;
  font-weight: 500;
  will-change: transform, opacity;
}

/* Buttons */
.btn-row { display: flex; gap: 8px; }
.btn-buggy, .btn-fixed {
  flex: 1;
  padding: 9px 14px;
  border-radius: 6px;
  font-size: 0.8rem;
  font-weight: 600;
  font-family: var(--font);
  cursor: pointer;
  transition: background 0.12s, color 0.12s, border-color 0.12s;
}
.btn-buggy {
  background: #fef2f2;
  color: var(--bad);
  border: 1px solid #fecaca;
}
.btn-buggy:hover { background: #fee2e2; }
.btn-fixed {
  background: #f0fdf4;
  color: var(--good);
  border: 1px solid #bbf7d0;
}
.btn-fixed:hover { background: #dcfce7; }

/* Trigger indicator */
.trigger-indicator {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.75rem;
  color: var(--text-3);
}
.ti-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--border);
  transition: background 0.2s;
}
.ti-dot.active { background: var(--good); }

/* Diff panel */
.diff-panel {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}
.diff-before, .diff-after {
  border-radius: 8px;
  overflow: hidden;
  border: 1px solid var(--border);
}
.diff-label {
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  padding: 8px 14px;
}
.diff-label--bad { background: #fef2f2; color: var(--bad); border-bottom: 1px solid #fecaca; }
.diff-label--good { background: #f0fdf4; color: var(--good); border-bottom: 1px solid #bbf7d0; }
.diff-before pre, .diff-after pre {
  padding: 14px;
  background: var(--bg-2);
  overflow-x: auto;
}
.diff-before code, .diff-after code {
  font-family: var(--mono);
  font-size: 0.72rem;
  line-height: 1.7;
  color: var(--text);
  white-space: pre;
}

/* Bug explanation */
.bug-explain {
  font-size: 0.875rem;
  color: var(--text-2);
  line-height: 1.7;
  padding: 16px 20px;
  background: var(--bg-2);
  border-radius: 8px;
  border: 1px solid var(--border);
}
.bug-explain code {
  font-family: var(--mono);
  font-size: 0.85em;
  background: var(--bg);
  border: 1px solid var(--border);
  padding: 1px 4px;
  border-radius: 3px;
}

/* Footer */
.footer-pad { padding: 60px 0 80px; }
.footer-pad .inner { display: flex; gap: 12px; flex-wrap: wrap; }
.btn-primary {
  display: inline-block;
  padding: 11px 24px;
  background: var(--accent);
  color: #fff;
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  border-radius: 6px;
  transition: background 0.15s;
}
.btn-primary:hover { background: #1d4ed8; }
.btn-ghost {
  display: inline-block;
  padding: 11px 24px;
  color: var(--text-2);
  text-decoration: none;
  font-size: 0.9rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  transition: border-color 0.15s, color 0.15s;
}
.btn-ghost:hover { border-color: #bbb; color: var(--text); }

@media (max-width: 640px) {
  .site-nav { padding: 14px 20px; }
  .inner { padding: 0 20px; }
  .hero .inner { padding-top: 48px; padding-bottom: 48px; }
  .hero h1 { font-size: 2.4rem; }
  .bug-layout { grid-template-columns: 1fr; }
  .diff-panel { grid-template-columns: 1fr; }
  .bug-section { padding: 48px 0; }
}