:root {
  --bg-primary: #0d1117;
  --bg-secondary: #161b22;
  --bg-tertiary: #21262d;
  --bg-hover: #30363d;
  --border: #30363d;
  --border-light: #21262d;
  --text-primary: #e6edf3;
  --text-secondary: #8b949e;
  --text-muted: #6e7681;
  --accent: #58a6ff;
  --accent-hover: #79c0ff;
  --accent-dim: rgba(88, 166, 255, 0.1);
  --green: #3fb950;
  --red: #f85149;
  --font-sans: 'Inter', -apple-system, sans-serif;
  --radius: 8px;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 15px; }
body { font-family: var(--font-sans); background: var(--bg-primary); color: var(--text-primary); height: 100vh; display: flex; flex-direction: column; overflow: hidden; }
a { color: var(--accent); text-decoration: none; }

/* Header */
header { display: flex; align-items: center; padding: 8px 16px; border-bottom: 1px solid var(--border); background: var(--bg-secondary); gap: 12px; flex-shrink: 0; }
.header-left { display: flex; align-items: center; gap: 8px; flex-shrink: 0; }
header h1 { font-size: 1.05rem; font-weight: 700; }
.header-center { flex: 1; max-width: 550px; }
.header-right { display: flex; gap: 6px; align-items: center; flex-shrink: 0; }
.header-right select { padding: 6px 8px; background: var(--bg-tertiary); border: 1px solid var(--border); border-radius: var(--radius); color: var(--text-primary); font-size: 0.8rem; font-family: var(--font-sans); }

.input-bar { display: flex; gap: 6px; }
.input-bar input { flex: 1; padding: 7px 12px; background: var(--bg-tertiary); border: 1px solid var(--border); border-radius: var(--radius); color: var(--text-primary); font-size: 0.85rem; font-family: var(--font-sans); outline: none; }
.input-bar input:focus { border-color: var(--accent); }
.input-bar input::placeholder { color: var(--text-muted); }

/* Buttons */
.btn { display: inline-flex; align-items: center; gap: 5px; padding: 6px 12px; border: 1px solid var(--border); border-radius: var(--radius); background: var(--bg-tertiary); color: var(--text-primary); font-size: 0.8rem; font-family: var(--font-sans); cursor: pointer; transition: all 0.15s; white-space: nowrap; }
.btn:hover { background: var(--bg-hover); }
.btn:disabled { opacity: 0.4; cursor: not-allowed; }
.btn-primary { background: var(--accent); border-color: var(--accent); color: #fff; font-weight: 600; }
.btn-primary:hover { background: var(--accent-hover); }
.btn-ghost { background: transparent; border-color: transparent; }
.btn-sm { padding: 4px 8px; font-size: 0.78rem; }

/* Loading */
.loading-bar { display: flex; align-items: center; gap: 10px; padding: 6px 16px; background: var(--bg-secondary); border-bottom: 1px solid var(--border); font-size: 0.8rem; color: var(--text-secondary); flex-shrink: 0; }
.spinner-sm { width: 14px; height: 14px; border: 2px solid var(--border); border-top-color: var(--accent); border-radius: 50%; animation: spin 0.6s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }

/* Empty State */
.empty-state { flex: 1; display: flex; flex-direction: column; align-items: center; justify-content: center; color: var(--text-muted); text-align: center; gap: 10px; }
.empty-state h2 { font-size: 1.15rem; color: var(--text-secondary); }
.empty-state p { font-size: 0.85rem; max-width: 480px; }
.example-links { display: flex; gap: 8px; margin-top: 8px; }
.example-link { padding: 5px 12px; background: var(--accent-dim); border-radius: var(--radius); font-size: 0.8rem; }

/* Main layout */
main { flex: 1; display: flex; overflow: hidden; }
.pane { display: flex; flex-direction: column; overflow: hidden; }
.pane-pdf { flex: 1; }
.pane-right { flex: 1; }
.pane-divider { width: 1px; background: var(--border); flex-shrink: 0; }


.pane-header { padding: 6px 12px; border-bottom: 1px solid var(--border-light); background: var(--bg-secondary); font-size: 0.78rem; color: var(--text-muted); display: flex; align-items: center; justify-content: space-between; flex-shrink: 0; }
.pane-body { flex: 1; overflow-y: auto; padding: 16px; font-size: 0.9rem; line-height: 1.8; }

/* PDF Area (outline + viewer) */
.pdf-area { flex: 1; display: flex; overflow: hidden; }
.pane-header-left { display: flex; align-items: center; gap: 6px; }
.outline-toggle svg { display: block; }

/* Outline Panel */
.outline-panel { width: 220px; background: var(--bg-secondary); border-right: 1px solid var(--border); display: flex; flex-direction: column; flex-shrink: 0; overflow: hidden; transition: width 0.2s ease, opacity 0.2s ease; }
.outline-panel.collapsed { width: 0; border-right: none; opacity: 0; pointer-events: none; }
.outline-header { padding: 8px 12px; font-size: 0.72rem; font-weight: 600; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.5px; display: flex; align-items: center; justify-content: space-between; border-bottom: 1px solid var(--border-light); flex-shrink: 0; }
.outline-count { font-weight: 400; color: var(--text-muted); font-size: 0.68rem; }
.outline-list { flex: 1; overflow-y: auto; list-style: none; padding: 4px 0; }
.outline-item { padding: 6px 12px; font-size: 0.76rem; color: var(--text-secondary); cursor: pointer; border-left: 2px solid transparent; transition: all 0.15s; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.outline-item:hover { background: var(--bg-tertiary); color: var(--text-primary); }
.outline-item.active { border-left-color: var(--accent); color: var(--accent); background: var(--accent-dim); }
.outline-item .section-num { color: var(--text-muted); margin-right: 4px; font-size: 0.68rem; }

/* PDF Viewer */
.pdf-viewer { flex: 1; overflow-y: auto; background: var(--bg-primary); display: flex; flex-direction: column; align-items: center; gap: 8px; padding: 8px; }
.pdf-viewer canvas { max-width: 100%; box-shadow: 0 2px 8px rgba(0,0,0,0.4); }
.pdf-controls { display: flex; align-items: center; gap: 6px; }
#zoom-level { font-size: 0.75rem; min-width: 36px; text-align: center; }

/* Pane tabs */
.pane-tabs { display: flex; gap: 2px; }
.pane-tab { padding: 4px 12px; background: none; border: none; border-bottom: 2px solid transparent; color: var(--text-muted); font-size: 0.78rem; font-family: var(--font-sans); cursor: pointer; }
.pane-tab:hover { color: var(--text-primary); }
.pane-tab.active { color: var(--accent); border-bottom-color: var(--accent); }
.pane-content { display: none; }
.pane-content.active { display: block; }
.pane-placeholder { color: var(--text-muted); text-align: center; padding: 40px 20px; font-size: 0.88rem; }
.pane-placeholder strong { color: var(--accent); }

/* Content area (markdown) */
.content-area { font-size: 0.9rem; line-height: 1.8; }
.content-area h1, .content-area h2, .content-area h3 { color: var(--accent); margin: 14px 0 6px; font-weight: 600; }
.content-area h2 { font-size: 1rem; }
.content-area p { margin-bottom: 8px; }
.content-area ul, .content-area ol { margin: 6px 0 6px 18px; }
.content-area li { margin-bottom: 3px; }
.content-area strong { color: var(--accent-hover); }
.content-area blockquote { border-left: 3px solid var(--accent); padding-left: 12px; color: var(--text-secondary); margin: 6px 0; }

.streaming::after { content: '▊'; animation: blink 0.8s step-end infinite; color: var(--accent); }
@keyframes blink { 50% { opacity: 0; } }

/* Copy button */
.copy-btn-wrap { position: relative; }
.copy-btn { position: sticky; top: 0; float: right; margin: 0 0 4px 8px; padding: 4px 10px; background: var(--bg-tertiary); border: 1px solid var(--border); border-radius: var(--radius); color: var(--text-secondary); font-size: 0.72rem; font-family: var(--font-sans); cursor: pointer; transition: all 0.15s; z-index: 2; }
.copy-btn:hover { background: var(--bg-hover); color: var(--text-primary); }
.copy-btn.copied { color: var(--green); border-color: var(--green); }

/* Paper metadata */
.paper-meta { padding: 10px 16px; background: var(--bg-secondary); border-bottom: 1px solid var(--border-light); font-size: 0.78rem; color: var(--text-secondary); line-height: 1.5; flex-shrink: 0; }
.paper-meta .meta-title { font-size: 0.88rem; font-weight: 600; color: var(--text-primary); margin-bottom: 4px; }
.paper-meta .meta-authors { color: var(--text-muted); margin-bottom: 2px; }
.paper-meta .meta-date { color: var(--text-muted); font-size: 0.72rem; }

/* Page indicator */
.page-indicator { font-size: 0.72rem; color: var(--text-muted); margin-left: 8px; }

/* Chat */
.chat-panel { position: fixed; right: 0; top: 0; bottom: 0; width: 360px; background: var(--bg-secondary); border-left: 1px solid var(--border); display: flex; flex-direction: column; z-index: 50; box-shadow: -4px 0 16px rgba(0,0,0,0.3); }
.chat-header { display: flex; align-items: center; justify-content: space-between; padding: 10px 14px; border-bottom: 1px solid var(--border); }
.chat-header h3 { font-size: 0.9rem; }
.chat-messages { flex: 1; overflow-y: auto; padding: 10px 14px; display: flex; flex-direction: column; gap: 8px; }
.chat-empty { display: flex; align-items: center; justify-content: center; height: 100%; color: var(--text-muted); font-size: 0.82rem; }
.chat-msg { padding: 8px 12px; border-radius: 10px; font-size: 0.82rem; line-height: 1.6; max-width: 88%; word-wrap: break-word; }
.chat-msg.user { align-self: flex-end; background: var(--accent); color: #fff; border-bottom-right-radius: 4px; }
.chat-msg.assistant { align-self: flex-start; background: var(--bg-tertiary); border: 1px solid var(--border-light); border-bottom-left-radius: 4px; }
.suggested-questions { display: flex; flex-wrap: wrap; gap: 5px; padding: 6px 14px; }
.suggestion { padding: 4px 10px; background: var(--accent-dim); border: 1px solid rgba(88,166,255,0.15); border-radius: 14px; color: var(--accent); font-size: 0.72rem; font-family: var(--font-sans); cursor: pointer; }
.suggestion:hover { background: rgba(88,166,255,0.2); }
.chat-input-bar { display: flex; gap: 6px; padding: 10px 14px; border-top: 1px solid var(--border); }
.chat-input-bar textarea { flex: 1; padding: 7px 10px; background: var(--bg-tertiary); border: 1px solid var(--border); border-radius: var(--radius); color: var(--text-primary); font-size: 0.82rem; font-family: var(--font-sans); resize: none; outline: none; max-height: 80px; }
.chat-input-bar textarea:focus { border-color: var(--accent); }

/* Toast */
.toast { position: fixed; bottom: 16px; left: 50%; transform: translateX(-50%); padding: 8px 18px; background: var(--bg-secondary); border: 1px solid var(--border); border-radius: var(--radius); font-size: 0.82rem; z-index: 200; box-shadow: 0 2px 8px rgba(0,0,0,0.3); animation: slideUp 0.3s ease; }
.toast.error { border-color: var(--red); color: var(--red); }
.toast.success { border-color: var(--green); color: var(--green); }
@keyframes slideUp { from { opacity: 0; transform: translateX(-50%) translateY(8px); } }

::-webkit-scrollbar { width: 5px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--bg-tertiary); border-radius: 3px; }
.hidden { display: none !important; }

@media (max-width: 768px) {
  header { flex-wrap: wrap; }
  .header-center { max-width: 100%; order: 3; flex-basis: 100%; }
  main { flex-direction: column; }
  .pane-divider { width: auto; height: 1px; }
  .pane-pdf, .pane-right { min-height: 40vh; }
  .chat-panel { width: 100%; }
  .outline-panel { width: 160px; }
}