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

:root {
  --sidebar-w: 260px;
  --topbar-h: 56px;

  --bg:          #0d0f14;
  --bg-surface:  #141720;
  --bg-elevated: #1a1e2b;
  --bg-code:     #111420;
  --border:      #252a3a;

  --text:        #e2e6f0;
  --text-muted:  #8892a4;
  --text-faint:  #545e72;

  --accent:      #6c8eff;
  --accent-dim:  rgba(108, 142, 255, 0.12);
  --accent-glow: rgba(108, 142, 255, 0.25);

  --green:   #4caf50;
  --red:     #f44336;
  --orange:  #ff9800;
  --blue:    #2196f3;
  --grey:    #9e9e9e;

  --radius-sm: 6px;
  --radius:    10px;
  --radius-lg: 16px;

  --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;

  --shadow: 0 4px 24px rgba(0, 0, 0, 0.4);
}

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-sans);
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  font-size: 15px;
}

/* ─── Sidebar ────────────────────────────────────────────────────── */
.sidebar {
  position: fixed;
  top: 0; left: 0; bottom: 0;
  width: var(--sidebar-w);
  background: var(--bg-surface);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  z-index: 100;
  transition: transform 0.28s cubic-bezier(.4,0,.2,1);
}

.sidebar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px 20px 16px;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}

.logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 18px;
  font-weight: 700;
  color: var(--text);
  text-decoration: none;
}

.logo-ring {
  color: var(--accent);
  font-size: 22px;
  line-height: 1;
}

.sidebar-close {
  display: none;
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 16px;
  cursor: pointer;
  padding: 4px 8px;
  border-radius: var(--radius-sm);
}
.sidebar-close:hover { background: var(--bg-elevated); color: var(--text); }

.nav-list {
  list-style: none;
  padding: 12px 0;
  flex: 1;
}

.nav-section {
  font-size: 10.5px;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-faint);
  padding: 16px 20px 6px;
}

.nav-list > li:first-child .nav-section,
.nav-section:first-child { padding-top: 8px; }

.nav-link {
  display: block;
  padding: 6px 20px;
  color: var(--text-muted);
  text-decoration: none;
  font-size: 13.5px;
  border-left: 2px solid transparent;
  transition: color 0.15s, background 0.15s, border-color 0.15s;
}

.nav-link:hover {
  color: var(--text);
  background: var(--accent-dim);
}

.nav-link.active {
  color: var(--accent);
  border-left-color: var(--accent);
  background: var(--accent-dim);
  font-weight: 500;
}

.sidebar-footer {
  padding: 16px 20px;
  border-top: 1px solid var(--border);
  flex-shrink: 0;
}

.gh-link {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  color: var(--text-muted);
  text-decoration: none;
  transition: color 0.15s;
}
.gh-link:hover { color: var(--text); }

/* ─── Topbar (mobile) ────────────────────────────────────────────── */
.topbar {
  display: none;
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--topbar-h);
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border);
  align-items: center;
  justify-content: space-between;
  padding: 0 16px;
  z-index: 101;
}

.topbar-logo { display: flex; align-items: center; gap: 7px; font-size: 16px; font-weight: 700; }

.menu-btn {
  background: none;
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 6px;
  color: var(--text-muted);
  transition: color 0.15s;
}
.menu-btn:hover { color: var(--text); }

.topbar-gh { color: var(--text-muted); transition: color 0.15s; }
.topbar-gh:hover { color: var(--text); }

/* ─── Backdrop ───────────────────────────────────────────────────── */
.backdrop {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.6);
  z-index: 99;
  backdrop-filter: blur(2px);
}
.backdrop.visible { display: block; }

/* ─── Main content ───────────────────────────────────────────────── */
.content {
  margin-left: var(--sidebar-w);
  max-width: 900px;
  padding: 0 48px 80px;
}

/* ─── Hero ───────────────────────────────────────────────────────── */
.hero {
  padding: 80px 0 60px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 60px;
}

.hero-badge {
  display: inline-block;
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
  background: var(--accent-dim);
  border: 1px solid var(--accent-glow);
  border-radius: 100px;
  padding: 4px 12px;
  margin-bottom: 20px;
}

.hero-title {
  font-size: clamp(40px, 6vw, 64px);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.1;
  margin-bottom: 20px;
  color: #fff;
}

.hero-ring {
  color: var(--accent);
  font-size: 0.9em;
}

.hero-sub {
  font-size: 18px;
  color: var(--text-muted);
  line-height: 1.6;
  margin-bottom: 36px;
  max-width: 520px;
}

.hero-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  padding: 10px 22px;
  border-radius: var(--radius);
  font-size: 14px;
  font-weight: 600;
  text-decoration: none;
  transition: all 0.15s;
  cursor: pointer;
}

.btn-primary {
  background: var(--accent);
  color: #fff;
  border: 1px solid var(--accent);
}
.btn-primary:hover { background: #5a7ef0; border-color: #5a7ef0; transform: translateY(-1px); box-shadow: 0 4px 16px var(--accent-glow); }

.btn-outline {
  background: transparent;
  color: var(--text);
  border: 1px solid var(--border);
}
.btn-outline:hover { background: var(--bg-elevated); border-color: var(--text-muted); transform: translateY(-1px); }

/* ─── Sections ───────────────────────────────────────────────────── */
.doc-section {
  margin-bottom: 72px;
  scroll-margin-top: 24px;
}

.doc-section h2 {
  font-size: 26px;
  font-weight: 700;
  color: #fff;
  letter-spacing: -0.02em;
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border);
}

.doc-section h3 {
  font-size: 15px;
  font-weight: 600;
  color: var(--text);
  margin: 28px 0 10px;
}

.doc-section p {
  color: var(--text-muted);
  margin-bottom: 16px;
  max-width: 680px;
}

.doc-section ul, .doc-section ol {
  padding-left: 20px;
  color: var(--text-muted);
  margin-bottom: 16px;
}

.doc-section li { margin-bottom: 6px; }

/* ─── Code blocks ────────────────────────────────────────────────── */
pre {
  background: var(--bg-code);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  overflow-x: auto;
  margin: 16px 0 24px;
  font-size: 13px;
  line-height: 1.65;
}

code {
  font-family: var(--font-mono);
  font-size: 13px;
  color: #c9d1e0;
}

p code, li code, td code {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1px 6px;
  font-size: 12.5px;
  color: #a8c4ff;
}

/* Syntax highlight (manual, no library) */
.lang-kotlin .kw   { color: #cc99cd; }
.lang-xml    .tag  { color: #6c8eff; }

/* ─── Tables ─────────────────────────────────────────────────────── */
.table-wrap { overflow-x: auto; margin: 16px 0 24px; }

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 13.5px;
}

thead tr { background: var(--bg-elevated); }

th, td {
  padding: 10px 14px;
  text-align: left;
  border-bottom: 1px solid var(--border);
  color: var(--text-muted);
}

th {
  font-size: 11.5px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-faint);
}

tr:last-child td { border-bottom: none; }
tbody tr:hover { background: var(--bg-elevated); }

/* ─── Callouts ───────────────────────────────────────────────────── */
.callout {
  display: flex;
  gap: 12px;
  padding: 14px 16px;
  border-radius: var(--radius);
  margin: 20px 0;
  font-size: 13.5px;
  color: var(--text-muted);
  border-left: 3px solid;
  line-height: 1.6;
}

.callout strong { color: var(--text); }
.callout a { color: var(--accent); }

.callout-info {
  background: rgba(33, 150, 243, 0.08);
  border-color: var(--blue);
}

.callout-warning {
  background: rgba(255, 152, 0, 0.08);
  border-color: var(--orange);
}

/* ─── Platform cards ─────────────────────────────────────────────── */
.platform-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 24px 0;
}

.platform-card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 24px;
  transition: border-color 0.2s;
}

.platform-card:hover { border-color: var(--accent); }
.platform-card.android { border-top: 3px solid #4caf50; }
.platform-card.ios     { border-top: 3px solid #6c8eff; }

.platform-icon { margin-bottom: 10px; color: var(--text-muted); }
.platform-card h3 { font-size: 15px; font-weight: 600; color: #fff; margin-bottom: 6px; }
.platform-card p  { font-size: 13px; color: var(--text-muted); margin: 0; }

/* ─── Feature grid ───────────────────────────────────────────────── */
.feature-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin: 24px 0;
}

.feature-item {
  display: flex;
  gap: 14px;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  align-items: flex-start;
}

.feature-icon { flex-shrink: 0; margin-top: 2px; color: var(--accent); }
.feature-item strong { display: block; font-size: 13.5px; color: var(--text); margin-bottom: 4px; }
.feature-item p { font-size: 12.5px; color: var(--text-muted); margin: 0; line-height: 1.5; }

/* ─── Architecture diagram ───────────────────────────────────────── */
.arch-diagram {
  margin: 24px 0;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.arch-split {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

.arch-layer {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
}

.arch-layer.shared { border-top: 2px solid var(--accent); }
.arch-layer.android { border-top: 2px solid var(--green); }
.arch-layer.ios     { border-top: 2px solid #6c8eff; }

.arch-label {
  display: block;
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-faint);
  margin-bottom: 10px;
}

.arch-boxes { display: flex; flex-wrap: wrap; gap: 6px; }

.arch-box {
  background: var(--bg-code);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 5px 10px;
  font-size: 12px;
  font-family: var(--font-mono);
  color: var(--text-muted);
}

/* ─── Call state list ────────────────────────────────────────────── */
.state-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 16px 0;
}

.state-item {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 6px 14px;
  border-radius: 100px;
  font-size: 12.5px;
  font-family: var(--font-mono);
  font-weight: 500;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
}

.state-item .dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
}

.state-item.dialing { color: #64b5f6; }
.state-item.dialing .dot { background: #2196f3; }
.state-item.ringing { color: #ffb74d; }
.state-item.ringing .dot { background: #ff9800; }
.state-item.active  { color: #81c784; }
.state-item.active  .dot { background: #4caf50; }
.state-item.holding { color: #b0bec5; }
.state-item.holding .dot { background: #9e9e9e; }
.state-item.ended   { color: #ef9a9a; }
.state-item.ended   .dot { background: #f44336; }

/* ─── Tag list ───────────────────────────────────────────────────── */
.tag-list { display: flex; flex-wrap: wrap; gap: 8px; margin: 12px 0; }
.tag {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 4px 10px;
  font-size: 12px;
  font-family: var(--font-mono);
  color: #a8c4ff;
}

/* ─── Notes list ─────────────────────────────────────────────────── */
.notes-list { list-style: none; padding: 0; }
.notes-list li {
  padding: 12px 16px 12px 44px;
  position: relative;
  border-bottom: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 13.5px;
}
.notes-list li:last-child { border-bottom: none; }
.notes-list li::before {
  content: "→";
  position: absolute;
  left: 16px;
  color: var(--accent);
  font-weight: 700;
}
.notes-list li strong { color: var(--text); }

/* ─── UI State preview ───────────────────────────────────────────── */
.ui-state-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
  margin: 28px 0;
}

.ui-state-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
}

.ui-state-label {
  font-size: 11px;
  color: var(--text-faint);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  font-weight: 600;
}

.ui-state-screen {
  width: 100%;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px 16px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
  min-height: 160px;
  justify-content: center;
}

.preview-title { font-size: 14px; font-weight: 600; color: var(--text); }
.preview-number, .preview-label {
  font-size: 12px;
  color: var(--text-muted);
}
.preview-label { font-size: 11px; text-transform: uppercase; letter-spacing: 0.05em; }
.preview-badge {
  font-size: 10px;
  font-weight: 600;
  letter-spacing: 0.06em;
  border-radius: 100px;
  padding: 2px 10px;
}
.active-badge { background: rgba(76, 175, 80, 0.15); color: var(--green); }

.preview-input {
  width: 100%;
  background: var(--bg-code);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 8px 10px;
  font-size: 12px;
  color: var(--text-faint);
  text-align: center;
}

.preview-btn {
  border-radius: var(--radius-sm);
  padding: 7px 18px;
  font-size: 12px;
  font-weight: 600;
  color: #fff;
  cursor: default;
}
.preview-btn.green { background: var(--green); }
.preview-btn.red   { background: var(--red); }

.preview-actions {
  display: flex;
  gap: 8px;
  width: 100%;
  justify-content: center;
}

.preview-chips { display: flex; gap: 6px; }
.chip {
  background: var(--bg-code);
  border: 1px solid var(--border);
  border-radius: 100px;
  padding: 3px 10px;
  font-size: 11px;
  color: var(--text-muted);
}

.ui-state-name {
  font-size: 11.5px;
  font-family: var(--font-mono);
  color: var(--accent);
}

/* ─── Footer ─────────────────────────────────────────────────────── */
.doc-footer {
  border-top: 1px solid var(--border);
  padding: 40px 0 20px;
  text-align: center;
  color: var(--text-faint);
  font-size: 13px;
}
.doc-footer a { color: var(--text-muted); text-decoration: none; }
.doc-footer a:hover { color: var(--text); }

/* ─── Scrollbar ──────────────────────────────────────────────────── */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--text-faint); }

/* ─── Responsive ─────────────────────────────────────────────────── */
@media (max-width: 900px) {
  .platform-grid,
  .feature-grid,
  .arch-split { grid-template-columns: 1fr; }

  .ui-state-grid { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 768px) {
  .topbar { display: flex; }

  .sidebar {
    transform: translateX(-100%);
    top: 0;
    z-index: 102;
  }

  .sidebar.open {
    transform: translateX(0);
    box-shadow: var(--shadow);
  }

  .sidebar-close { display: block; }

  .content {
    margin-left: 0;
    padding: 80px 20px 60px;
  }

  .hero { padding: 40px 0 40px; }
  .hero-title { font-size: 36px; }
  .hero-sub { font-size: 15px; }

  .doc-section h2 { font-size: 22px; }

  .ui-state-grid { grid-template-columns: 1fr; }
}

@media (max-width: 480px) {
  .hero-actions { flex-direction: column; }
  .btn { justify-content: center; }
  .state-list { flex-direction: column; }
}