:root {
  --bg: #f8f9fb;
  --bg-card: #ffffff;
  --bg-card-hover: #f0f2f5;
  --text: #1a1a2e;
  --text-muted: #5a5f72;
  --border: #d8dce6;
  --primary: #4f46e5;
  --accent: #e85d26;
}
* { margin: 0; padding: 0; box-sizing: border-box; }
body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
}
a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

/* Nav */
nav {
  display: flex; align-items: center; justify-content: space-between;
  padding: 0.75rem 2rem;
  background: var(--bg-card);
  border-bottom: 1px solid var(--border);
  position: sticky; top: 0; z-index: 100;
  box-shadow: 0 1px 3px rgba(0,0,0,0.04);
}
nav .brand {
  font-size: 1.1rem; font-weight: 700; color: var(--text);
  display: flex; align-items: center; gap: 0.5rem;
}
nav .brand span { color: var(--accent); }
nav .links { display: flex; gap: 1.5rem; align-items: center; }
nav .links a {
  color: var(--text-muted); font-size: 0.85rem; font-weight: 500;
  transition: color 0.15s;
}
nav .links a:hover, nav .links a.active { color: var(--text); text-decoration: none; }

/* Hero */
.hero { text-align: center; padding: 2.5rem 2rem 1rem; }
.hero h1 { font-size: 2rem; font-weight: 800; letter-spacing: -0.02em; color: var(--text); }
.hero h1 span { color: var(--accent); }
.hero p { color: var(--text-muted); max-width: 600px; margin: 0.5rem auto 0; font-size: 0.95rem; }
.hero .meta { margin-top: 0.75rem; font-size: 0.8rem; color: var(--text-muted); }
.hero .meta strong { color: var(--text); }

/* Diagram */
.diagram-wrap {
  position: relative; margin: 1rem auto; max-width: 1200px;
  background: var(--bg-card); border: 1px solid var(--border); border-radius: 12px; overflow: hidden;
  box-shadow: 0 2px 8px rgba(0,0,0,0.06);
}
.diagram-toolbar {
  position: absolute; top: 0.75rem; right: 0.75rem; z-index: 20;
  display: flex; gap: 0.25rem;
  background: var(--bg-card); border: 1px solid var(--border); border-radius: 8px; padding: 0.25rem;
  box-shadow: 0 2px 6px rgba(0,0,0,0.06);
}
.diagram-toolbar button {
  width: 32px; height: 32px; border: 1px solid var(--border); border-radius: 6px;
  background: var(--bg-card); color: var(--text-muted); font-size: 0.9rem;
  cursor: pointer; display: flex; align-items: center; justify-content: center;
  transition: all 0.15s; font-family: monospace;
}
.diagram-toolbar button:hover { background: var(--bg-card-hover); color: var(--text); border-color: var(--primary); }
.diagram-toolbar button.fullscreen-btn { width: auto; padding: 0 0.6rem; font-family: system-ui; font-size: 0.75rem; font-weight: 600; gap: 0.3rem; }
.diagram-container { width: 100%; min-height: 900px; }
.diagram-container svg { width: 100%; height: 100%; display: block; cursor: grab; }
.diagram-container svg:active { cursor: grabbing; }

/* Tooltip */
.arch-tooltip {
  position: fixed; background: #1a1a2e; color: #fff;
  padding: 0.6rem 0.85rem; border-radius: 8px; font-size: 0.78rem; line-height: 1.45;
  width: 240px; text-align: center; z-index: 200; pointer-events: none;
  box-shadow: 0 4px 16px rgba(0,0,0,0.2); opacity: 0; transition: opacity 0.15s;
}

/* Export bar */
.export-bar { display: flex; justify-content: center; gap: 0.75rem; padding: 1rem 2rem; flex-wrap: wrap; }
.export-bar button, .export-bar a.btn {
  padding: 0.5rem 1.25rem; border: 1px solid var(--border); border-radius: 8px;
  background: var(--bg-card); color: var(--text); font-size: 0.82rem; font-weight: 600;
  cursor: pointer; transition: all 0.15s; display: inline-flex; align-items: center; gap: 0.4rem;
  box-shadow: 0 1px 3px rgba(0,0,0,0.04);
}
.export-bar button:hover, .export-bar a.btn:hover { background: var(--primary); border-color: var(--primary); color: #fff; text-decoration: none; }

/* Stats banner */
.stats-banner { display: flex; justify-content: center; gap: 2rem; padding: 1rem 2rem; flex-wrap: wrap; }
.stat { text-align: center; }
.stat .num { font-size: 1.5rem; font-weight: 800; color: var(--accent); }
.stat .label { font-size: 0.72rem; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.08em; }

/* Page sections */
.page-section { max-width: 900px; margin: 0 auto; padding: 2rem 2rem 3rem; }
.page-section h2 { font-size: 1.5rem; font-weight: 700; margin-bottom: 1rem; border-bottom: 2px solid var(--border); padding-bottom: 0.5rem; }
.page-section h3 { font-size: 1.1rem; font-weight: 600; margin: 1.5rem 0 0.5rem; color: var(--accent); }
.page-section p { color: var(--text-muted); margin-bottom: 0.75rem; }
.page-section ul { margin-left: 1.25rem; margin-bottom: 1rem; color: var(--text-muted); }
.page-section li { margin-bottom: 0.35rem; }
.page-section code { background: #eef0f5; border: 1px solid var(--border); border-radius: 4px; padding: 0.1rem 0.4rem; font-size: 0.85em; color: var(--primary); }
.page-section pre { background: #eef0f5; border: 1px solid var(--border); border-radius: 8px; padding: 1rem; overflow-x: auto; font-size: 0.82rem; color: var(--text-muted); margin-bottom: 1rem; }

/* Connection cards */
.conn-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(380px, 1fr)); gap: 0.75rem; margin-top: 1rem; }
.conn-card { background: var(--bg-card); border: 1px solid var(--border); border-radius: 10px; padding: 1rem; transition: border-color 0.15s; box-shadow: 0 1px 3px rgba(0,0,0,0.04); }
.conn-card:hover { border-color: var(--primary); }
.conn-card .conn-label { font-size: 0.75rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.08em; margin-bottom: 0.25rem; }
.conn-card .conn-path { font-size: 0.85rem; font-weight: 600; color: var(--text); margin-bottom: 0.35rem; }
.conn-card .conn-desc { font-size: 0.78rem; color: var(--text-muted); line-height: 1.5; }
.conn-card .conn-tag { display: inline-block; font-size: 0.65rem; font-weight: 700; padding: 0.15rem 0.5rem; border-radius: 4px; margin-top: 0.5rem; text-transform: uppercase; letter-spacing: 0.05em; }
.tag-autonomous { background: rgba(232,93,38,0.1); color: #c94d1e; }
.tag-deterministic { background: rgba(79,70,229,0.1); color: #4f46e5; }
.tag-bidirectional { background: rgba(37,99,235,0.1); color: #1d4ed8; }
.tag-transport { background: rgba(20,184,166,0.1); color: #0d9488; }

/* Value route cards */
.value-route { background: var(--bg-card); border: 1px solid var(--border); border-left: 4px solid var(--accent); border-radius: 10px; padding: 1.25rem; margin-bottom: 1rem; box-shadow: 0 1px 3px rgba(0,0,0,0.04); }
.value-route h4 { font-size: 1rem; font-weight: 700; color: var(--text); margin-bottom: 0.5rem; }
.value-route p { font-size: 0.85rem; }

/* Layer list */
.layer-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 0.75rem; margin-top: 1rem; }
.layer-card { background: var(--bg-card); border: 1px solid var(--border); border-radius: 10px; padding: 1rem; border-top: 3px solid var(--primary); box-shadow: 0 1px 3px rgba(0,0,0,0.04); }
.layer-card h4 { font-size: 0.95rem; font-weight: 700; margin-bottom: 0.25rem; }
.layer-card .layer-nodes { font-size: 0.78rem; color: var(--text-muted); }
.layer-card .node-chip { display: inline-block; background: rgba(79,70,229,0.08); border: 1px solid rgba(79,70,229,0.18); border-radius: 4px; padding: 0.1rem 0.4rem; margin: 0.15rem 0.15rem 0 0; font-size: 0.72rem; color: var(--primary); }

/* Tab navigation */
.tab-nav { display: flex; gap: 0; border-bottom: 2px solid var(--border); margin-bottom: 1.5rem; }
.tab-btn { padding: 0.6rem 1.25rem; border: none; background: none; color: var(--text-muted); font-size: 0.85rem; font-weight: 600; cursor: pointer; border-bottom: 2px solid transparent; margin-bottom: -2px; transition: all 0.15s; }
.tab-btn:hover { color: var(--text); }
.tab-btn.active { color: var(--accent); border-bottom-color: var(--accent); }
.tab-panel { display: none; }
.tab-panel.active { display: block; }

/* Footer */
footer { text-align: center; padding: 2rem; border-top: 1px solid var(--border); color: var(--text-muted); font-size: 0.8rem; }
footer a { color: var(--primary); }

/* Fullscreen */
.diagram-wrap:fullscreen { background: #fff; border-radius: 0; }
.diagram-wrap:fullscreen .diagram-container { min-height: 100vh; }

@media (max-width: 768px) {
  nav { padding: 0.5rem 1rem; flex-direction: column; gap: 0.5rem; }
  .hero h1 { font-size: 1.4rem; }
  .stats-banner { gap: 1rem; }
  .conn-grid { grid-template-columns: 1fr; }
  .layer-grid { grid-template-columns: 1fr; }
  .page-section { padding: 1.5rem 1rem; }
}