:root {
  --bg: #0b1220;
  --surface: #141d2e;
  --surface-2: #243047;
  --surface-3: #1a2538;
  --text: #f1f5f9;
  --text-dim: #94a3b8;
  --text-faint: #64748b;
  --primary: #3b82f6;
  --primary-hover: #2563eb;
  --primary-soft: rgba(59, 130, 246, 0.15);
  --accent: #10b981;
  --accent-soft: rgba(16, 185, 129, 0.15);
  --warn: #f59e0b;
  --error: #ef4444;
  --border: #243047;
  --border-strong: #334155;
  --radius: 12px;
  --radius-sm: 8px;
  --radius-lg: 16px;
  --drawer-w: 280px;
  --topbar-h: 56px;
  --bottomnav-h: 60px;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.35);
  --shadow-lg: 0 12px 32px rgba(0,0,0,0.5);
  --safe-bottom: env(safe-area-inset-bottom, 0px);
  --safe-top: env(safe-area-inset-top, 0px);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  height: 100%;
  width: 100%;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, "Helvetica Neue", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  -webkit-text-size-adjust: 100%;
  -webkit-tap-highlight-color: transparent;
}
button { -webkit-tap-highlight-color: transparent; }

.screen { min-height: 100vh; min-height: 100dvh; display: flex; flex-direction: column; }
.hidden { display: none !important; }

/* ============ LOGIN ============ */
#login-view {
  align-items: center;
  justify-content: center;
  padding: 24px;
}
.login-card {
  background: var(--surface);
  border-radius: var(--radius-lg);
  padding: 32px 28px;
  width: 100%;
  max-width: 380px;
  border: 1px solid var(--border);
  box-shadow: var(--shadow-lg);
}
.login-card h1 { margin: 0 0 6px; font-size: 28px; }
.login-card .subtitle { margin: 0 0 24px; color: var(--text-dim); font-size: 14px; }
.login-card input[type="password"] {
  width: 100%;
  padding: 12px 14px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text);
  font-size: 16px;
  margin-bottom: 12px;
}
.login-card input:focus { outline: none; border-color: var(--primary); }
.login-card button {
  width: 100%;
  padding: 12px;
  background: var(--primary);
  color: white;
  border: none;
  border-radius: var(--radius);
  font-size: 16px;
  font-weight: 500;
  cursor: pointer;
}
.error {
  background: #7f1d1d;
  color: #fecaca;
  padding: 10px;
  border-radius: var(--radius);
  margin-top: 12px;
  font-size: 14px;
}

/* ============ LANDING ============ */
#landing-view {
  align-items: center;
  justify-content: center;
  padding: 24px;
  padding-top: max(24px, var(--safe-top));
  background: radial-gradient(ellipse at top, #1e3a8a22, transparent 60%), var(--bg);
}
.landing-content { max-width: 720px; width: 100%; text-align: center; }
.landing-title { font-size: clamp(22px, 6vw, 32px); margin: 0 0 8px; }
.landing-sub { color: var(--text-dim); margin: 0 0 32px; }
.learner-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 16px;
  margin-bottom: 32px;
}
.learner-card {
  background: var(--surface);
  border: 2px solid var(--border);
  border-radius: 20px;
  padding: 32px 24px;
  cursor: pointer;
  color: var(--text);
  transition: all 0.2s;
  box-shadow: var(--shadow-md);
}
.learner-card:hover {
  transform: translateY(-4px);
  border-color: var(--primary);
  box-shadow: var(--shadow-lg);
}
.learner-card.chuyen:hover { border-color: var(--primary); }
.learner-card.kid:hover { border-color: var(--warn); }
.learner-icon { font-size: 56px; margin-bottom: 12px; }
.learner-name { font-size: 20px; font-weight: 700; margin-bottom: 6px; }
.learner-desc { color: var(--text-dim); font-size: 14px; margin-bottom: 12px; }
.learner-subjects { color: var(--text-faint); font-size: 13px; }
.landing-footer { margin-top: 20px; }

/* ============ WORKSPACE ============ */
.ws {
  display: grid;
  grid-template-rows: var(--topbar-h) 1fr var(--bottomnav-h);
  height: 100vh;
  height: 100dvh;
  overflow: hidden;
}
.ws-topbar {
  display: flex;
  align-items: center;
  padding: 0 12px;
  padding-top: max(0px, var(--safe-top));
  height: calc(var(--topbar-h) + var(--safe-top));
  background: rgba(20, 29, 46, 0.9);
  backdrop-filter: saturate(160%) blur(12px);
  -webkit-backdrop-filter: saturate(160%) blur(12px);
  border-bottom: 1px solid var(--border);
  gap: 10px;
  z-index: 10;
}
.ws-brand {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 600;
  font-size: 15px;
  min-width: 0;
  flex: 1;
}
#ws-learner-icon { font-size: 20px; }
#ws-title {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.ws-controls { display: flex; gap: 6px; align-items: center; }

.seg-control { display: inline-flex; background: var(--bg); border: 1px solid var(--border); border-radius: 10px; padding: 3px; }
.seg-control button {
  background: transparent;
  color: var(--text-dim);
  border: none;
  padding: 6px 11px;
  cursor: pointer;
  border-radius: 8px;
  font-size: 13px;
  font-weight: 500;
}
.seg-control button.active { background: var(--primary); color: white; box-shadow: var(--shadow-sm); }

.ghost {
  background: transparent;
  color: var(--text-dim);
  border: 1px solid var(--border);
  padding: 7px 12px;
  border-radius: 10px;
  cursor: pointer;
  font-size: 13.5px;
  transition: all 0.15s;
}
.ghost:hover { color: var(--text); border-color: var(--text-dim); background: var(--surface-2); }
.icon-only-btn {
  width: 38px;
  height: 38px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0;
  font-size: 18px;
}
.mobile-only { display: none; }
.full-width { width: 100%; }

/* ============ DRAWER (left) ============ */
.drawer {
  position: fixed;
  top: calc(var(--topbar-h) + var(--safe-top));
  left: 0;
  bottom: 0;
  width: var(--drawer-w);
  background: var(--surface);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  z-index: 8;
  transition: transform 0.25s cubic-bezier(.4, 0, .2, 1);
  padding-bottom: var(--safe-bottom);
  overflow-y: auto;
}
.drawer-header { flex-shrink: 0; position: sticky; top: 0; background: var(--surface); z-index: 2; }
.drawer-section { flex-shrink: 0 !important; flex: none !important; min-height: 0 !important; }
.drawer-history { max-height: none !important; overflow: visible !important; }
.drawer.collapsed { transform: translateX(-100%); }
.drawer-header {
  padding: 12px;
  border-bottom: 1px solid var(--border);
  display: flex;
  gap: 8px;
  align-items: center;
}
.new-chat-btn {
  flex: 1;
  background: var(--primary);
  color: white;
  border: none;
  padding: 10px 14px;
  border-radius: 10px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
}
.new-chat-btn:hover { background: var(--primary-hover); }
.drawer-nav {
  padding: 8px;
  display: flex;
  flex-direction: column;
  gap: 2px;
  border-bottom: 1px solid var(--border);
}
.drawer-nav button {
  background: transparent;
  border: none;
  color: var(--text);
  padding: 10px 12px;
  text-align: left;
  border-radius: 8px;
  cursor: pointer;
  font-size: 14px;
  display: flex;
  align-items: center;
  gap: 10px;
}
.drawer-nav button:hover { background: var(--surface-2); }
.drawer-nav button.active {
  background: var(--primary-soft);
  color: white;
  font-weight: 500;
}
.drawer-nav button .nav-badge {
  margin-left: auto;
  background: var(--error);
  color: white;
  font-size: 11px;
  padding: 1px 6px;
  border-radius: 8px;
}
.drawer-nav button .nav-badge.gold { background: var(--warn); color: #1e293b; }

.drawer-section { padding: 8px; flex: 1; min-height: 0; display: flex; flex-direction: column; }
.drawer-section-head {
  background: transparent;
  border: none;
  color: var(--text-dim);
  padding: 8px 10px;
  text-align: left;
  border-radius: 6px;
  cursor: pointer;
  font-size: 12px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
}
.drawer-section-head .chev { transition: transform 0.15s; font-size: 10px; }
.drawer-section-head.open .chev { transform: rotate(90deg); }
.drawer-section-head:hover { color: var(--text); }
.drawer-history {
  flex: 1;
  overflow-y: auto;
  padding-top: 6px;
}
.drawer-subsection h5 {
  margin: 8px 4px 4px;
  color: var(--text-dim);
  font-size: 11.5px;
  font-weight: 600;
  letter-spacing: 0.3px;
}
.session-list { list-style: none; margin: 0; padding: 0; }
.session-item {
  display: flex;
  align-items: center;
  padding: 8px 10px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 13px;
  color: var(--text);
  gap: 6px;
}
.session-item:hover { background: var(--surface-2); }
.session-item.active { background: var(--primary); }
.session-item .session-title {
  flex: 1;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.session-item .session-del {
  background: transparent;
  border: none;
  color: var(--text-dim);
  font-size: 14px;
  cursor: pointer;
  padding: 0 4px;
  opacity: 0;
}
.session-item:hover .session-del,
.session-item.active .session-del { opacity: 1; }
.empty-hint { color: var(--text-dim); font-size: 12px; padding: 6px 10px; font-style: italic; }

.drawer-footer { padding: 10px; border-top: 1px solid var(--border); display: flex; flex-direction: column; gap: 6px; }

/* ============ MAIN ============ */
.ws-main {
  grid-row: 2;
  position: relative;
  margin-left: var(--drawer-w);
  overflow: hidden;
  display: flex;
  flex-direction: column;
}
.ws-pane {
  display: none;
  flex: 1;
  min-height: 0;
  overflow-y: auto;
  flex-direction: column;
}
.ws-pane.active { display: flex; }

.pane-header {
  padding: 16px 20px 12px;
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
  position: sticky;
  top: 0;
  background: var(--bg);
  z-index: 5;
  border-bottom: 1px solid var(--border);
}
.pane-header h2 {
  margin: 0;
  font-size: 18px;
  flex: 1;
  min-width: 0;
}

/* ============ CHAT VIEW ============ */
.ws-pane[data-pane="chat"] { padding: 0; }
#messages { flex: 1; overflow-y: auto; padding: 16px; }
.msg-wrap { max-width: 920px; margin: 0 auto; }
.msg { margin-bottom: 18px; animation: fadeUp 0.2s ease-out; }
.msg.user { text-align: right; }
.msg-bubble {
  display: inline-block;
  max-width: 88%;
  padding: 12px 14px;
  border-radius: 16px;
  text-align: left;
  word-wrap: break-word;
  line-height: 1.55;
}
.msg.user .msg-bubble {
  background: var(--primary);
  color: white;
  border-bottom-right-radius: 6px;
  box-shadow: var(--shadow-sm);
}
.msg.ai .msg-bubble {
  background: var(--surface);
  border: 1px solid var(--border);
  border-bottom-left-radius: 6px;
  width: 100%;
}
@keyframes fadeUp {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}
.msg.user .msg-img {
  max-width: 220px;
  margin-bottom: 8px;
  border-radius: 10px;
  display: block;
  margin-left: auto;
  cursor: zoom-in;
}
.msg.user .msg-img:hover { transform: scale(1.02); }
.msg.user .image-hint { font-size: 12px; color: var(--text-dim); margin-bottom: 4px; }

.msg-bubble h1, .msg-bubble h2, .msg-bubble h3 {
  margin: 16px 0 8px;
  color: #fde68a;
  font-size: 15px;
  font-weight: 600;
}
.msg-bubble h2:first-child, .msg-bubble h3:first-child { margin-top: 0; }
.msg-bubble p { margin: 8px 0; line-height: 1.55; }
.msg-bubble ol, .msg-bubble ul { padding-left: 24px; line-height: 1.55; }
.msg-bubble code { background: var(--bg); padding: 2px 6px; border-radius: 4px; font-size: 13px; }
.msg-bubble pre { background: var(--bg); padding: 12px; border-radius: 8px; overflow-x: auto; }

/* Markdown blockquote callouts (cho lesson highlight) */
.msg-bubble blockquote, .roadmap-content blockquote, .type-body-content blockquote, #pane-theory-md blockquote {
  margin: 12px 0;
  padding: 10px 14px;
  border-left: 4px solid var(--primary);
  background: rgba(59, 130, 246, 0.08);
  border-radius: 4px;
  color: var(--text);
}
.msg-bubble blockquote p, .roadmap-content blockquote p, .type-body-content blockquote p, #pane-theory-md blockquote p {
  margin: 4px 0;
}
/* Warning callout (>⚠️) */
.roadmap-content blockquote:has(p:first-child:first-letter):has(strong),
.type-body-content blockquote, #pane-theory-md blockquote { font-size: 13.5px; }
.msg-bubble blockquote strong, .roadmap-content blockquote strong, .type-body-content blockquote strong, #pane-theory-md blockquote strong { color: #fde68a; }
/* Highlight key formula */
.roadmap-content strong, .type-body-content strong, #pane-theory-md strong { color: #fde68a; }
.roadmap-content em, .type-body-content em { color: #93c5fd; }
.roadmap-content h3, .type-body-content h3, #pane-theory-md h3 { color: #6ee7b7; margin-top: 18px; }
.roadmap-content h4, .type-body-content h4, #pane-theory-md h4 { color: #fde68a; margin-top: 14px; }
.roadmap-content hr, .type-body-content hr { border: none; border-top: 1px dashed var(--border); margin: 16px 0; }
.katex-display { overflow-x: auto; overflow-y: hidden; }

.msg.ai .meta {
  display: flex;
  gap: 12px;
  color: var(--text-dim);
  font-size: 12px;
  margin-top: 8px;
  flex-wrap: wrap;
}
.msg.ai .sources {
  margin-top: 8px;
  font-size: 12px;
  color: var(--text-dim);
  border-top: 1px dashed var(--border);
  padding-top: 8px;
}
.msg.ai .sources strong { color: var(--text); }

/* SVG diagrams from AI */
.msg-bubble .diagram, .roadmap-content .diagram, .type-body-content .diagram, #pane-theory-md .diagram {
  background: white;
  padding: 12px;
  border-radius: 8px;
  margin: 14px 0;
  display: block;
  width: 100%;
  max-width: 480px;
  overflow-x: auto;
  box-shadow: 0 1px 3px rgba(0,0,0,0.2);
}
.diagram svg {
  display: block;
  width: 100%;
  height: auto;
  max-height: 400px;
}

/* ============ COMPOSER ============ */
.composer {
  background: rgba(20, 29, 46, 0.92);
  backdrop-filter: saturate(160%) blur(12px);
  -webkit-backdrop-filter: saturate(160%) blur(12px);
  border-top: 1px solid var(--border);
  padding: 10px 14px;
  padding-bottom: calc(10px + var(--safe-bottom));
  flex-shrink: 0;
}
.composer-row {
  display: flex;
  gap: 8px;
  align-items: flex-end;
  max-width: 920px;
  margin: 0 auto;
}
#question-input {
  flex: 1;
  padding: 11px 14px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 20px;
  color: var(--text);
  font-family: inherit;
  font-size: 15px;
  resize: vertical;
  min-height: 44px;
  max-height: 180px;
  line-height: 1.45;
}
#question-input:focus { outline: none; border-color: var(--primary); }
.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 50%;
  cursor: pointer;
  font-size: 20px;
  flex-shrink: 0;
  transition: all 0.15s;
}
.icon-btn:hover { border-color: var(--text-dim); background: var(--surface-2); }
.icon-btn:active { transform: scale(0.95); }
#send-btn {
  padding: 0 18px;
  height: 44px;
  background: var(--primary);
  color: white;
  border: none;
  border-radius: 22px;
  font-weight: 600;
  cursor: pointer;
  font-size: 14.5px;
  flex-shrink: 0;
}
#send-btn:disabled { opacity: 0.4; cursor: not-allowed; }

.image-preview {
  max-width: 920px;
  margin: 0 auto 8px;
  position: relative;
  display: inline-block;
}
.image-preview img { max-width: 200px; max-height: 180px; border-radius: 8px; }
.remove-image {
  position: absolute;
  top: -8px;
  right: -8px;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  background: var(--error);
  color: white;
  border: none;
  font-size: 18px;
  cursor: pointer;
}
.status-bar {
  max-width: 920px;
  margin: 8px auto 0;
  color: var(--text-dim);
  font-size: 12px;
  text-align: center;
  min-height: 16px;
}

.typing { display: inline-flex; gap: 4px; }
.typing span { width: 8px; height: 8px; background: var(--text-dim); border-radius: 50%; animation: bounce 1.4s infinite; }
.typing span:nth-child(2) { animation-delay: 0.2s; }
.typing span:nth-child(3) { animation-delay: 0.4s; }
@keyframes bounce { 0%, 60%, 100% { transform: translateY(0); opacity: 0.4; } 30% { transform: translateY(-6px); opacity: 1; } }

/* ============ LIGHTBOX ============ */
.lightbox {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.92);
  z-index: 200;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
  cursor: zoom-out;
}
.lightbox img { max-width: 100%; max-height: 100%; object-fit: contain; }
.lightbox-close {
  position: fixed;
  top: 16px;
  right: 16px;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: rgba(255,255,255,0.15);
  color: white;
  border: none;
  font-size: 20px;
  cursor: pointer;
}

/* ============ ROADMAP VIEW ============ */
.ws-pane[data-pane="roadmap"] {
  overflow: hidden;
}
.ws-pane[data-pane="roadmap"] .roadmap-body {
  flex: 1;
  display: flex;
  min-height: 0;
  overflow: hidden;
}
.roadmap-tree {
  width: 320px;
  border-right: 1px solid var(--border);
  overflow-y: auto;
  min-height: 0;
  padding: 8px 0;
  flex-shrink: 0;
  background: var(--surface);
}
.roadmap-section { margin-bottom: 12px; }
.roadmap-section-title { padding: 10px 14px 4px; color: var(--text); font-size: 13.5px; font-weight: 600; }
.roadmap-section-intro { padding: 0 14px 6px; font-size: 11.5px; color: var(--text-dim); font-style: italic; }
.roadmap-node {
  padding: 8px 14px 8px 20px;
  cursor: pointer;
  font-size: 13.5px;
  display: flex;
  align-items: center;
  gap: 8px;
  border-left: 3px solid transparent;
}
.roadmap-node:hover { background: var(--surface-2); }
.roadmap-node.active { background: var(--surface-2); border-left-color: var(--primary); }
.roadmap-node-info { flex: 1; min-width: 0; }
.roadmap-node-title { white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.roadmap-node-blurb { font-size: 11px; color: var(--text-dim); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.roadmap-node-status {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--border);
  flex-shrink: 0;
}
.roadmap-node[data-status="learning"] .roadmap-node-status { background: var(--warn); }
.roadmap-node[data-status="done"] .roadmap-node-status { background: var(--accent); }
.roadmap-node .cached-mark { font-size: 11px; color: var(--text-dim); margin-left: 4px; }

.roadmap-content {
  flex: 1;
  overflow-y: auto;
  overflow-x: hidden;
  min-height: 0;
  min-width: 0;
  max-width: 100%;
  padding: 20px 24px 80px;
  overflow-wrap: anywhere;
  word-break: break-word;
}
.roadmap-content > *, #pane-theory-md > *, .type-body-content > * { max-width: 100%; box-sizing: border-box; }
.roadmap-content img, .roadmap-content svg, .type-body-content svg, #pane-theory-md svg { max-width: 100%; height: auto; }
.roadmap-content p, .roadmap-content li, .type-body-content p, .type-body-content li, #pane-theory-md p, #pane-theory-md li {
  overflow-wrap: anywhere;
  word-break: break-word;
  max-width: 100%;
}
/* KaTeX display block must scroll horizontal if too wide */
.roadmap-content .katex-display, .type-body-content .katex-display, #pane-theory-md .katex-display {
  overflow-x: auto;
  overflow-y: hidden;
  max-width: 100%;
  margin: 12px 0;
}
.roadmap-content .katex-display > .katex, .type-body-content .katex-display > .katex, #pane-theory-md .katex-display > .katex {
  max-width: 100%;
}
.roadmap-content pre, .type-body-content pre, #pane-theory-md pre {
  background: var(--code-bg, #0b1220);
  padding: 12px;
  border-radius: 8px;
  overflow-x: auto;
  white-space: pre-wrap;
  word-break: break-word;
  font-size: 13px;
}
.roadmap-content code, .type-body-content code, #pane-theory-md code {
  background: var(--bg);
  padding: 1px 5px;
  border-radius: 4px;
  font-size: 13px;
  word-break: break-word;
}
.roadmap-content ul, .roadmap-content ol,
.type-body-content ul, .type-body-content ol,
#pane-theory-md ul, #pane-theory-md ol {
  padding-left: 22px;
}
.roadmap-content li, .type-body-content li, #pane-theory-md li {
  margin-bottom: 4px;
  overflow-wrap: anywhere;
}
.roadmap-content table, .type-body-content table {
  display: block;
  overflow-x: auto;
  max-width: 100%;
}
/* KaTeX overflow on mobile */
.roadmap-content .katex-display, .type-body-content .katex-display, #pane-theory-md .katex-display {
  overflow-x: auto;
  overflow-y: hidden;
  max-width: 100%;
}
.roadmap-empty { color: var(--text-dim); text-align: center; padding: 60px 20px; }
.roadmap-content h1 { margin: 0 0 6px; font-size: clamp(18px, 4.5vw, 24px); }

.roadmap-toolbar {
  display: flex;
  gap: 6px;
  margin-bottom: 12px;
  overflow-x: auto;
  padding-bottom: 4px;
  scrollbar-width: none;
}
.roadmap-toolbar::-webkit-scrollbar { display: none; }
.roadmap-toolbar .status-btn {
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 7px 12px;
  border-radius: 18px;
  font-size: 12.5px;
  cursor: pointer;
  white-space: nowrap;
  flex-shrink: 0;
}
.roadmap-toolbar .status-btn.active[data-value="todo"] { background: #374151; color: white; }
.roadmap-toolbar .status-btn.active[data-value="learning"] { background: var(--warn); color: white; }
.roadmap-toolbar .status-btn.active[data-value="done"] { background: var(--accent); color: white; }

.advanced-wrap { position: relative; display: inline-block; }
.advanced-menu {
  position: fixed;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 6px;
  min-width: 220px;
  z-index: 200;
  box-shadow: var(--shadow-lg);
}
.advanced-menu button {
  display: block;
  width: 100%;
  text-align: left;
  background: transparent;
  border: none;
  color: var(--text);
  padding: 10px 12px;
  cursor: pointer;
  border-radius: 6px;
  font-size: 13.5px;
}
.advanced-menu button:hover { background: var(--surface-2); }

.lesson-tabs {
  display: flex;
  gap: 4px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 14px;
  overflow-x: auto;
  scrollbar-width: thin;
}
.lesson-tabs button {
  background: transparent;
  color: var(--text-dim);
  border: none;
  padding: 8px 14px;
  cursor: pointer;
  font-size: 13.5px;
  border-bottom: 2px solid transparent;
  white-space: nowrap;
}
.lesson-tabs button.active { color: var(--text); border-bottom-color: var(--primary); font-weight: 500; }
.rag-badge {
  display: inline-block;
  font-size: 9px;
  padding: 1px 6px;
  border-radius: 8px;
  background: var(--accent);
  color: white;
  font-weight: 700;
  margin-left: 4px;
  letter-spacing: 0.4px;
}
.rag-result-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent);
  border-radius: 10px;
  margin-bottom: 12px;
  overflow: hidden;
}
.rag-result-head {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 8px;
  padding: 10px 14px;
  background: rgba(16,185,129,0.05);
  cursor: pointer;
  user-select: none;
  flex-wrap: wrap;
}
.rag-result-head:hover { background: rgba(16,185,129,0.10); }
.rag-result-source {
  font-size: 12.5px;
  color: var(--accent);
  font-weight: 500;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  flex: 1;
  min-width: 0;
}
.rag-result-score {
  font-size: 11px;
  color: var(--text-dim);
  background: var(--bg);
  padding: 2px 7px;
  border-radius: 8px;
  flex-shrink: 0;
}
.rag-result-arrow {
  color: var(--text-dim);
  font-size: 11px;
  transition: transform 0.15s;
  flex-shrink: 0;
}
.rag-result-card.expanded .rag-result-arrow { transform: rotate(180deg); }
.rag-result-preview {
  padding: 10px 14px;
  font-size: 13px;
  color: var(--text-dim);
  line-height: 1.5;
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
  text-overflow: ellipsis;
  cursor: pointer;
}
.rag-result-card.expanded .rag-result-preview { display: none; }
.rag-result-body {
  display: none;
  padding: 12px 14px 4px;
  border-top: 1px solid var(--border);
}
.rag-result-card.expanded .rag-result-body { display: block; }
.rag-result-text {
  font-size: 13.5px;
  line-height: 1.65;
  color: var(--text);
  white-space: pre-wrap;
  word-break: break-word;
}
.rag-result-actions {
  display: flex;
  gap: 6px;
  padding: 10px 0 4px;
  border-top: 1px dashed var(--border);
  margin-top: 12px;
  flex-wrap: wrap;
}
.rag-result-actions button {
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 6px 12px;
  border-radius: 6px;
  cursor: pointer;
  font-size: 12.5px;
}
.rag-result-actions button.primary {
  background: var(--primary);
  color: white;
  border-color: var(--primary);
}
.rag-result-actions button:hover { border-color: var(--text-dim); }
.rag-result-actions button.primary:hover { background: var(--primary-hover); }
.rag-source-list {
  background: rgba(16,185,129,0.08);
  border-left: 3px solid var(--accent);
  padding: 10px 14px;
  border-radius: 6px;
  margin-bottom: 14px;
  font-size: 12.5px;
  color: var(--text-dim);
}
.rag-source-list strong { color: var(--accent); }
.rag-source-list ul { margin: 6px 0 0; padding-left: 20px; }
.rag-source-list li { margin-bottom: 3px; }

/* Practice bank UI */
.practice-bank-body { padding: 16px 20px 80px; max-width: 100%; box-sizing: border-box; }
.practice-search-bar {
  display: flex;
  gap: 8px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}
.practice-search-bar input[type="text"] {
  flex: 1;
  min-width: 200px;
  padding: 10px 14px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  font-size: 14px;
}
.practice-search-bar input[type="text"]:focus { outline: none; border-color: var(--primary); }
.practice-search-bar select {
  padding: 10px 12px;
  background: var(--bg);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 13.5px;
}
/* Difficulty selector */
.diff-selector {
  display: flex;
  gap: 6px;
  margin: 14px 0;
  padding: 10px 12px;
  background: var(--surface);
  border-radius: 10px;
  border: 1px solid var(--border);
  align-items: center;
  flex-wrap: wrap;
}
.diff-selector .diff-label {
  color: var(--text-dim);
  font-size: 12.5px;
  margin-right: 4px;
}
.diff-selector button {
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 6px 12px;
  border-radius: 8px;
  font-size: 12.5px;
  cursor: pointer;
}
.diff-selector button.active {
  background: var(--primary);
  color: white;
  border-color: var(--primary);
  font-weight: 500;
}
.diff-selector button[data-diff="very-hard"].active { background: var(--error); border-color: var(--error); }
.diff-selector button[data-diff="hard"].active { background: var(--warn); border-color: var(--warn); }
.diff-selector button[data-diff="easy"].active { background: var(--accent); border-color: var(--accent); }

.rag-similar-section {
  margin-top: 14px;
  padding-top: 14px;
  border-top: 1px dashed var(--border);
}
.rag-similar-btn {
  background: var(--bg);
  border: 1px solid var(--accent);
  color: var(--accent);
  padding: 7px 14px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 13px;
  font-weight: 500;
}
.rag-similar-btn:hover { background: rgba(16,185,129,0.1); }
.rag-similar-btn:disabled { opacity: 0.6; cursor: not-allowed; }

.practice-search-bar #practice-search-btn {
  padding: 10px 18px;
  background: var(--accent);
  color: white;
  border: none;
  border-radius: 8px;
  font-weight: 500;
  cursor: pointer;
}
.lesson-pane { display: none; }
.lesson-pane.active { display: block; }

.types-toolbar { display: flex; gap: 8px; margin-bottom: 12px; flex-wrap: wrap; }
.types-toolbar button {
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 6px 10px;
  border-radius: 6px;
  cursor: pointer;
  font-size: 12.5px;
}
.type-card {
  border: 1px solid var(--border);
  border-radius: 10px;
  margin-bottom: 10px;
  overflow: hidden;
  background: var(--bg);
}
.type-header {
  padding: 11px 14px;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 10px;
  user-select: none;
  flex-wrap: wrap;
}
.type-header:hover { background: var(--surface-2); }
.type-arrow {
  display: inline-block;
  transition: transform 0.15s;
  color: var(--text-dim);
  font-size: 11px;
  width: 12px;
}
.type-card.expanded .type-arrow { transform: rotate(90deg); }
.type-name {
  font-weight: 500;
  flex: 1 1 auto;
  min-width: 0;
  overflow-wrap: anywhere;
}
.type-blurb {
  color: var(--text-dim);
  font-size: 12px;
  font-style: italic;
  flex: 1 1 100%;
  margin-left: 22px;
  margin-top: -2px;
}
.type-status-pill {
  display: inline-flex;
  align-items: center;
  font-size: 11px;
  padding: 1px 7px;
  border-radius: 10px;
  background: var(--bg);
  color: var(--text-dim);
}
.type-status-pill.learning { color: var(--warn); background: rgba(245,158,11,0.15); }
.type-status-pill.done { color: var(--accent); background: rgba(16,185,129,0.15); }

.type-body { display: none; padding: 0 14px 14px 28px; border-top: 1px solid var(--border); }
.type-card.expanded .type-body { display: block; }
.type-controls {
  margin-top: 14px;
  padding: 12px;
  background: var(--surface);
  border-radius: 8px;
  border: 1px solid var(--border);
}
.type-controls > div { display: flex; gap: 6px; flex-wrap: wrap; align-items: center; margin-bottom: 6px; }
.type-controls > div:last-child { margin-bottom: 0; }
.type-controls .label { color: var(--text-dim); font-size: 12px; }
.type-status-btn, .type-rate-btn {
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 4px 10px;
  border-radius: 6px;
  cursor: pointer;
  font-size: 12px;
}
.type-status-btn.active[data-value="todo"] { background: #374151; color: white; }
.type-status-btn.active[data-value="learning"] { background: var(--warn); color: white; }
.type-status-btn.active[data-value="done"] { background: var(--accent); color: white; }
.next-review-info { color: var(--text-dim); font-size: 11.5px; }

.more-controls {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 14px;
  padding: 12px;
  background: var(--surface);
  border-radius: 10px;
}
.more-controls select {
  flex: 1;
  min-width: 200px;
  padding: 8px;
  background: var(--bg);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 13.5px;
}
.more-controls button {
  background: var(--accent);
  color: white;
  border: none;
  padding: 8px 16px;
  border-radius: 6px;
  cursor: pointer;
  font-weight: 500;
}
.extra-examples {
  margin-top: 16px;
  padding-top: 14px;
  border-top: 1px dashed var(--accent);
}
.extra-examples-meta { color: var(--text-dim); font-size: 11.5px; margin-bottom: 8px; }

.roadmap-meta {
  color: var(--text-dim);
  font-size: 11.5px;
  margin-top: 18px;
  padding-top: 10px;
  border-top: 1px dashed var(--border);
}

/* ============ STATS / DOCS / REVIEW / KID VIEWS ============ */
/* Pane scroll: pane itself is the vertical scroller */
.ws-pane[data-pane="cost"],
.ws-pane[data-pane="docs"],
.ws-pane[data-pane="review"],
.ws-pane[data-pane="kid-streak"],
.ws-pane[data-pane="kid-practice"],
.ws-pane[data-pane="exam"] {
  overflow-y: auto;
  overflow-x: hidden;
  -webkit-overflow-scrolling: touch;
}
.stats-body, .indexed-body, .kid-body, .exam-body {
  padding: 16px 20px 100px;
  max-width: 100%;
  box-sizing: border-box;
}
.stats-body > *, .indexed-body > *, .kid-body > *, .exam-body > * {
  max-width: 100%;
  box-sizing: border-box;
}
.stat-card { max-width: 100%; }
.stats-table {
  width: 100%;
  display: block;
  overflow-x: auto;
}
.indexed-tabs {
  display: flex;
  gap: 6px;
  overflow-x: auto;
  margin-left: auto;
}
.indexed-tabs button {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 5px 12px;
  border-radius: 6px;
  font-size: 12.5px;
  cursor: pointer;
  white-space: nowrap;
}
.indexed-tabs button.active { background: var(--primary); color: white; border-color: var(--primary); }
.indexed-summary { padding: 12px 20px; color: var(--text-dim); font-size: 13px; border-bottom: 1px solid var(--border); }
.indexed-summary strong { color: var(--text); }
.indexed-table { width: 100%; border-collapse: collapse; font-size: 13px; }
.indexed-table th {
  background: var(--bg);
  color: var(--text-dim);
  padding: 8px 12px;
  text-align: left;
  font-weight: 500;
  position: sticky;
  top: 0;
}
.indexed-table td { padding: 8px 12px; border-bottom: 1px solid var(--border); }
.indexed-table .file-name { font-weight: 500; }
.indexed-table .file-path { color: var(--text-dim); font-size: 11px; }

.badge {
  display: inline-block;
  padding: 1px 8px;
  border-radius: 10px;
  font-size: 11px;
  font-weight: 500;
}
.badge-toan { background: #1e3a8a; color: #93c5fd; }
.badge-ly { background: #7c2d12; color: #fdba74; }
.badge-anh { background: #3b0764; color: #d8b4fe; }
.badge-sach { background: #064e3b; color: #6ee7b7; }
.badge-de_thi { background: #581c87; color: #d8b4fe; }

.stat-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 14px 16px;
  margin-bottom: 12px;
}
.stat-card h4 { margin: 0 0 8px; color: var(--text-dim); font-size: 12px; text-transform: uppercase; letter-spacing: 0.5px; }
.stat-card .big-cost { font-size: 28px; font-weight: 700; color: var(--accent); }
.stat-card .sub-row { display: flex; gap: 16px; flex-wrap: wrap; color: var(--text-dim); font-size: 12px; margin-top: 6px; }
.stat-card .sub-row b { color: var(--text); }
.stats-table { width: 100%; border-collapse: collapse; font-size: 12.5px; }
.stats-table th { background: var(--bg); padding: 6px 10px; text-align: left; color: var(--text-dim); font-weight: 500; }
.stats-table td { padding: 6px 10px; border-bottom: 1px solid var(--border); }
.stats-cost { color: var(--accent); font-weight: 500; }

/* ============ EXAM VIEW ============ */
.exam-body { padding: 16px 20px 40px; overflow-y: auto; flex: 1; }
.exam-tiles {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 10px;
}
.exam-tile {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 14px;
  text-align: left;
  cursor: pointer;
  color: var(--text);
  transition: all 0.15s;
}
.exam-tile:hover { border-color: var(--primary); transform: translateY(-1px); }
.exam-tile.primary { border-color: var(--accent); background: rgba(16,185,129,0.08); }
.tile-icon { font-size: 24px; }
.tile-title { font-weight: 600; font-size: 14px; }
.tile-sub { font-size: 12px; color: var(--text-dim); }

.exam-question {
  background: var(--surface-3);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 14px 16px;
  margin-bottom: 12px;
}
.exam-question.graded.correct { border-color: var(--accent); background: rgba(16,185,129,0.05); }
.exam-question.graded.wrong { border-color: var(--error); background: rgba(239,68,68,0.05); }
.exam-q-num { color: var(--text-dim); font-size: 12px; font-weight: 600; margin-bottom: 4px; }
.exam-q-prompt { font-size: 14.5px; line-height: 1.5; margin-bottom: 8px; }
.exam-q-options { display: flex; flex-direction: column; gap: 6px; }
.exam-q-option {
  padding: 8px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  background: var(--bg);
  font-size: 13.5px;
}
.exam-q-option.selected { border-color: var(--primary); background: var(--primary-soft); }
.exam-q-option.correct { border-color: var(--accent); background: var(--accent-soft); }
.exam-q-option.wrong { border-color: var(--error); background: rgba(239,68,68,0.1); }
.exam-q-input {
  width: 100%;
  padding: 10px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  font-family: inherit;
  font-size: 14px;
  resize: vertical;
  min-height: 60px;
}
.exam-q-correct-pill {
  display: inline-block;
  padding: 2px 8px;
  background: var(--accent-soft);
  color: var(--accent);
  border-radius: 10px;
  font-size: 11px;
  margin-top: 6px;
}
.exam-q-wrong-pill {
  display: inline-block;
  padding: 2px 8px;
  background: rgba(239,68,68,0.15);
  color: #fca5a5;
  border-radius: 10px;
  font-size: 11px;
  margin-top: 6px;
}
.exam-q-explanation {
  margin-top: 8px;
  padding: 8px 10px;
  background: var(--bg);
  border-left: 3px solid var(--primary);
  border-radius: 4px;
  font-size: 12.5px;
  color: var(--text-dim);
  line-height: 1.5;
}
.exam-passage {
  background: var(--surface-3);
  border-left: 3px solid var(--primary);
  padding: 12px 14px;
  margin-bottom: 14px;
  border-radius: 8px;
  font-size: 14px;
  line-height: 1.6;
}
.exam-toolbar {
  display: flex;
  gap: 8px;
  margin-bottom: 14px;
  position: sticky;
  top: 0;
  background: var(--bg);
  padding: 8px 0;
  z-index: 2;
}
.exam-submit-btn {
  background: var(--accent);
  color: white;
  border: none;
  padding: 10px 20px;
  border-radius: 10px;
  font-weight: 600;
  cursor: pointer;
}
.exam-result {
  background: var(--primary-soft);
  border: 1px solid var(--primary);
  border-radius: 12px;
  padding: 16px;
  margin-bottom: 16px;
}
.exam-score { font-size: 28px; font-weight: 700; color: var(--accent); }

/* ============ KID VIEWS ============ */
.kid-body { padding: 16px 20px 40px; overflow-y: auto; flex: 1; }
.kid-launcher h2 { font-size: 22px; text-align: center; margin: 12px 0; color: #fde68a; }
.kid-tiles {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
  gap: 12px;
  margin-top: 12px;
}
.kid-tile {
  background: var(--surface);
  border: 2px solid var(--border);
  border-radius: 16px;
  padding: 18px 12px;
  cursor: pointer;
  text-align: center;
  color: var(--text);
  transition: all 0.15s;
}
.kid-tile:hover { transform: translateY(-2px) scale(1.02); border-color: var(--warn); }
.kid-tile .ki-icon { font-size: 36px; display: block; margin-bottom: 6px; }
.kid-tile .ki-title { font-weight: 600; font-size: 14.5px; }

.kid-daily-card {
  background: linear-gradient(135deg, #f97316, #fbbf24);
  color: #1e293b;
  border-radius: 16px;
  padding: 14px 16px;
  margin-bottom: 14px;
  text-align: center;
  box-shadow: var(--shadow-md);
}
.kid-daily-title { font-size: 16px; font-weight: 700; }
.kid-daily-dots { font-size: 22px; letter-spacing: 4px; margin: 8px 0; }
.kid-daily-hint { font-size: 12.5px; opacity: 0.85; }
.kid-weeks { background: rgba(255,255,255,0.6); margin-top: 10px; padding: 6px 10px; border-radius: 10px; font-size: 13px; }
.kid-week-banner {
  background: linear-gradient(135deg, #ec4899, #f97316);
  color: white;
  padding: 14px;
  text-align: center;
  font-weight: 700;
  font-size: 17px;
  border-radius: 14px;
  margin-bottom: 12px;
  animation: pulse 1.2s infinite alternate;
}
@keyframes pulse {
  from { transform: scale(1); }
  to { transform: scale(1.02); }
}

.kid-stats {
  background: var(--surface);
  border-radius: 12px;
  padding: 12px 16px;
  margin: 14px 0;
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
  justify-content: space-around;
}
.kid-stat { text-align: center; }
.kid-stat .num { font-size: 22px; font-weight: 700; color: var(--warn); }
.kid-stat .lbl { font-size: 11px; color: var(--text-dim); }

.kid-question {
  background: var(--surface-3);
  border: 2px solid var(--border);
  border-radius: 16px;
  padding: 16px;
  margin-bottom: 12px;
}
.kid-question.graded.correct { border-color: var(--accent); background: rgba(16,185,129,0.1); }
.kid-question.graded.wrong { border-color: var(--error); background: rgba(239,68,68,0.08); }
.kid-q-num {
  background: var(--warn);
  color: #1e293b;
  font-weight: 700;
  padding: 2px 10px;
  border-radius: 10px;
  font-size: 12px;
  display: inline-block;
  margin-bottom: 6px;
}
.kid-q-prompt { font-size: 17px; line-height: 1.5; margin-bottom: 12px; }
.kid-q-options { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; }
.kid-q-option {
  padding: 12px;
  border: 2px solid var(--border);
  border-radius: 12px;
  cursor: pointer;
  background: var(--bg);
  font-size: 15px;
  font-weight: 500;
}
.kid-q-option:hover { border-color: var(--warn); }
.kid-q-option.selected { border-color: var(--primary); background: var(--primary-soft); }
.kid-q-option.correct { border-color: var(--accent); background: var(--accent-soft); }
.kid-q-option.wrong { border-color: var(--error); background: rgba(239,68,68,0.15); }
.kid-q-explanation {
  margin-top: 10px;
  padding: 10px 12px;
  background: rgba(251,191,36,0.1);
  border-left: 3px solid var(--warn);
  border-radius: 6px;
  font-size: 14px;
}
.kid-submit-btn {
  background: linear-gradient(135deg, var(--accent), #059669);
  color: white;
  border: none;
  padding: 14px 28px;
  border-radius: 14px;
  font-weight: 700;
  font-size: 16px;
  cursor: pointer;
  width: 100%;
  margin-top: 8px;
}
.kid-summary {
  background: linear-gradient(135deg, rgba(251,191,36,0.2), rgba(59,130,246,0.15));
  border: 2px solid var(--warn);
  border-radius: 18px;
  padding: 24px;
  text-align: center;
  margin-bottom: 16px;
}
.kid-summary .big-score { font-size: 48px; font-weight: 800; color: var(--warn); }
.kid-summary .stars-row { font-size: 32px; margin: 8px 0; letter-spacing: 4px; }
.kid-summary .msg { font-size: 16px; margin-top: 8px; }

/* ============ BOTTOM NAV (mobile + desktop) ============ */
.bottom-nav {
  display: flex;
  grid-row: 3;
  height: calc(var(--bottomnav-h) + var(--safe-bottom));
  padding-bottom: var(--safe-bottom);
  background: rgba(20, 29, 46, 0.96);
  backdrop-filter: saturate(160%) blur(12px);
  -webkit-backdrop-filter: saturate(160%) blur(12px);
  border-top: 1px solid var(--border);
  justify-content: space-around;
  z-index: 9;
}
.bottom-nav button {
  flex: 1;
  background: transparent;
  border: none;
  color: var(--text-dim);
  padding: 6px 4px 8px;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2px;
  font-size: 11.5px;
  position: relative;
  transition: color 0.15s, background 0.15s;
  border-radius: 0;
}
.bottom-nav button .bn-icon { font-size: 22px; transition: transform 0.15s; }
.bottom-nav button .bn-label { white-space: nowrap; font-weight: 500; }
.bottom-nav button:hover { color: var(--text); background: rgba(59,130,246,0.06); }
.bottom-nav button.active {
  color: var(--primary);
  background: var(--primary-soft);
}
.bottom-nav button.active::before {
  content: "";
  position: absolute;
  top: 0;
  left: 12%;
  right: 12%;
  height: 3px;
  background: var(--primary);
  border-radius: 0 0 4px 4px;
}
.bottom-nav button.active .bn-icon { transform: scale(1.08); }
.bottom-nav button .bn-badge {
  position: absolute;
  top: 4px;
  right: calc(50% - 22px);
  background: var(--error);
  color: white;
  font-size: 10px;
  padding: 1px 5px;
  border-radius: 8px;
  line-height: 1.2;
  font-weight: 600;
}
.bottom-nav button .bn-badge.gold { background: var(--warn); color: #1e293b; }

/* Desktop: max-width container for bottom nav */
@media (min-width: 769px) {
  .bottom-nav {
    justify-content: center;
    gap: 4px;
  }
  .bottom-nav button {
    flex: 0 0 auto;
    min-width: 100px;
    max-width: 140px;
  }
}

.backdrop {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.55);
  z-index: 7;
}

/* ============ CHAT WELCOME / EMPTY STATE ============ */
.chat-welcome {
  max-width: 720px;
  margin: 40px auto;
  padding: 32px 24px;
  text-align: center;
}
.chat-welcome h2 {
  margin: 0 0 8px;
  font-size: 24px;
  color: #fde68a;
}
.chat-welcome .welcome-sub {
  color: var(--text-dim);
  margin-bottom: 24px;
}
.chat-welcome .prompt-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 10px;
  margin-bottom: 28px;
}
.chat-welcome .prompt-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 14px;
  cursor: pointer;
  text-align: left;
  color: var(--text);
  font-size: 13.5px;
  line-height: 1.4;
  transition: all 0.15s;
}
.chat-welcome .prompt-card:hover {
  border-color: var(--primary);
  background: var(--surface-2);
  transform: translateY(-1px);
}
.chat-welcome .prompt-card .pc-icon {
  font-size: 18px;
  margin-right: 6px;
}
.chat-welcome .tips {
  color: var(--text-dim);
  font-size: 12.5px;
  line-height: 1.6;
}

/* ============ MOBILE LAYOUT ============ */
@media (max-width: 768px) {
  :root { --drawer-w: 86vw; }
  .mobile-only { display: inline-flex; }

  .ws-main { margin-left: 0; }

  .drawer {
    top: 0;
    height: 100vh;
    height: 100dvh;
    z-index: 30;
    box-shadow: 4px 0 24px rgba(0,0,0,0.5);
    max-width: 320px;
  }
  .drawer.collapsed { transform: translateX(-100%); }
  .drawer:not(.collapsed) ~ .backdrop { display: block; }

  /* Mobile: tree và content thành 2 trang riêng, fill toàn body, scroll độc lập */
  .ws-pane[data-pane="roadmap"] .roadmap-body {
    display: block;
    position: relative;
    overflow: hidden;
  }
  .ws-pane[data-pane="roadmap"] .roadmap-body .roadmap-tree,
  .ws-pane[data-pane="roadmap"] .roadmap-body .roadmap-content {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    width: 100%;
    max-width: 100vw;
    border-right: none;
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
  }
  .ws-pane[data-pane="roadmap"] .roadmap-body[data-mobile-view="tree"] .roadmap-content { display: none; }
  .ws-pane[data-pane="roadmap"] .roadmap-body[data-mobile-view="content"] .roadmap-tree { display: none; }

  .pane-header { padding: 12px 14px; }
  .pane-header h2 { font-size: 16px; }
  #messages { padding: 12px 12px 4px; }
  .composer { padding: 8px 10px; padding-bottom: calc(8px + var(--safe-bottom)); }
  #question-input { font-size: 16px; }
  .kid-tiles, .kid-q-options { grid-template-columns: 1fr 1fr; }
  .kid-q-options { grid-template-columns: 1fr; }
  .ws-controls .seg-control button { padding: 5px 8px; font-size: 12px; }
  .ws-controls .seg-control { flex-shrink: 0; }
  /* Subject seg hide trên topbar mobile (đã có trong drawer) */
  #ws-subject-seg { display: none !important; }
  #ws-mode-seg { display: none; }
  .ws-brand { font-size: 13.5px; }
  .chat-welcome { padding: 20px 16px; margin: 20px auto; }
}

/* Subject + Mode seg trong drawer (cho mobile + desktop khi cần) */
.drawer-subject-seg, .drawer-mode-seg { display: none; }

@media (max-width: 768px) {
  .drawer-subject-seg {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
    padding: 10px 12px;
    border-bottom: 1px solid var(--border);
  }
  .drawer-subject-seg button {
    flex: 1 1 calc(50% - 6px);
    background: var(--bg);
    color: var(--text-dim);
    border: 1px solid var(--border);
    padding: 8px;
    border-radius: 8px;
    font-size: 13px;
    cursor: pointer;
  }
  .drawer-subject-seg button.active {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
    font-weight: 500;
  }
  .drawer-mode-seg {
    display: block;
    padding: 10px 12px;
    border-bottom: 1px solid var(--border);
  }
  .drawer-mode-seg .drawer-mode-label {
    color: var(--text-dim);
    font-size: 11.5px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 6px;
  }
  .drawer-mode-seg button {
    width: 100%;
    background: var(--bg);
    color: var(--text-dim);
    border: 1px solid var(--border);
    padding: 9px;
    border-radius: 8px;
    font-size: 13px;
    cursor: pointer;
    margin-bottom: 4px;
    text-align: left;
  }
  .drawer-mode-seg button.active {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
    font-weight: 500;
  }
}