/* ===== CSS Variables / Design Tokens ===== */
:root {
  --bg-primary: #f7f7f8;
  --bg-secondary: #ffffff;
  --bg-sidebar: #171717;
  --bg-sidebar-hover: #2a2a2a;
  --bg-sidebar-active: #333333;
  --bg-user-msg: #f7f7f8;
  --bg-ai-msg: #ffffff;
  --bg-code: #1e1e2e;
  --bg-composer: #ffffff;
  --bg-composer-inner: #f4f4f5;

  --text-primary: #1a1a1a;
  --text-secondary: #6b6b6b;
  --text-sidebar: #ececec;
  --text-sidebar-muted: #8e8e8e;
  --text-code: #cdd6f4;
  --text-inverse: #ffffff;

  --border: #e5e5e5;
  --border-light: #f0f0f0;
  --border-sidebar: #2a2a2a;

  --accent: #0d9668;
  --accent-hover: #0b7d56;
  --accent-light: #ecfdf5;
  --accent-glow: rgba(13, 150, 104, 0.15);

  --danger: #ef4444;

  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;

  --shadow-sm: 0 1px 2px rgba(0,0,0,.04);
  --shadow-md: 0 4px 12px rgba(0,0,0,.06);
  --shadow-lg: 0 8px 30px rgba(0,0,0,.08);

  --sidebar-width: 280px;
  --topbar-h: 56px;
  --composer-max: 680px;
  --chat-max: 740px;

  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;

  --transition: 180ms ease;
}

/* ===== Reset ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { height: 100%; -webkit-text-size-adjust: 100%; }
body {
  height: 100%;
  font-family: var(--font-sans);
  font-size: 15px;
  line-height: 1.6;
  color: var(--text-primary);
  background: var(--bg-primary);
  display: flex;
  overflow: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

button, input, textarea, select {
  font-family: inherit;
  font-size: inherit;
  border: none;
  outline: none;
  background: none;
}
button { cursor: pointer; }

/* ===== Sidebar ===== */
.sidebar {
  width: var(--sidebar-width);
  height: 100vh;
  background: var(--bg-sidebar);
  color: var(--text-sidebar);
  display: flex;
  flex-direction: column;
  flex-shrink: 0;
  z-index: 100;
  transition: transform var(--transition);
}

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

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 1.05rem;
  letter-spacing: -0.01em;
}
.logo svg { color: var(--accent); }

.sidebar-search {
  padding: 12px 16px 8px;
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--bg-sidebar-hover);
  margin: 12px 12px 0;
  border-radius: var(--radius-md);
}
.sidebar-search svg { color: var(--text-sidebar-muted); flex-shrink: 0; }
.sidebar-search input {
  flex: 1;
  background: transparent;
  color: var(--text-sidebar);
  font-size: 0.875rem;
}
.sidebar-search input::placeholder { color: var(--text-sidebar-muted); }

.conv-list {
  flex: 1;
  overflow-y: auto;
  padding: 8px;
  display: flex;
  flex-direction: column;
  gap: 2px;
}
.conv-list::-webkit-scrollbar { width: 4px; }
.conv-list::-webkit-scrollbar-thumb { background: var(--border-sidebar); border-radius: 4px; }

.conv-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 12px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: background var(--transition);
  font-size: 0.875rem;
  color: var(--text-sidebar-muted);
  position: relative;
}
.conv-item:hover { background: var(--bg-sidebar-hover); color: var(--text-sidebar); }
.conv-item.active { background: var(--bg-sidebar-active); color: var(--text-sidebar); }
.conv-item svg { flex-shrink: 0; opacity: 0.6; }
.conv-item-title {
  flex: 1;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.conv-item .delete-btn {
  opacity: 0;
  color: var(--text-sidebar-muted);
  padding: 2px;
  border-radius: 4px;
  transition: opacity var(--transition), color var(--transition);
}
.conv-item:hover .delete-btn { opacity: 1; }
.conv-item .delete-btn:hover { color: var(--danger); }

.sidebar-footer {
  padding: 12px 16px;
  border-top: 1px solid var(--border-sidebar);
}

.model-selector {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--bg-sidebar-hover);
  padding: 8px 12px;
  border-radius: var(--radius-sm);
}
.model-selector svg { color: var(--accent); flex-shrink: 0; }
.model-selector select {
  flex: 1;
  background: transparent;
  color: var(--text-sidebar);
  font-size: 0.82rem;
  cursor: pointer;
}
.model-selector select option { background: var(--bg-sidebar); color: var(--text-sidebar); }

/* ===== Main Area ===== */
.main {
  flex: 1;
  display: flex;
  flex-direction: column;
  height: 100vh;
  min-width: 0;
  position: relative;
}

/* Mobile topbar */
.topbar {
  display: none;
  align-items: center;
  gap: 12px;
  padding: 10px 16px;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  height: var(--topbar-h);
}
.top-title {
  flex: 1;
  font-weight: 600;
  font-size: 0.95rem;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

/* ===== Chat Box ===== */
.chat-box {
  flex: 1;
  overflow-y: auto;
  scroll-behavior: smooth;
}
.chat-box::-webkit-scrollbar { width: 6px; }
.chat-box::-webkit-scrollbar-thumb { background: #ddd; border-radius: 6px; }
.chat-box::-webkit-scrollbar-thumb:hover { background: #ccc; }

/* Welcome */
.welcome {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 60px 24px;
  min-height: 100%;
  animation: fadeUp 400ms ease;
}
.welcome-icon {
  width: 72px;
  height: 72px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--accent-light);
  border-radius: 50%;
  margin-bottom: 20px;
  color: var(--accent);
}
.welcome h2 {
  font-size: 1.6rem;
  font-weight: 700;
  margin-bottom: 8px;
  letter-spacing: -0.02em;
}
.welcome p {
  color: var(--text-secondary);
  max-width: 420px;
  margin-bottom: 28px;
  font-size: 0.95rem;
}

.suggestions {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 10px;
  max-width: 500px;
  width: 100%;
}

.suggestion {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 14px 16px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  font-size: 0.85rem;
  color: var(--text-secondary);
  text-align: left;
  transition: all var(--transition);
}
.suggestion:hover {
  border-color: var(--accent);
  color: var(--accent);
  box-shadow: var(--shadow-sm);
  transform: translateY(-1px);
}
.suggestion svg { flex-shrink: 0; }

/* ===== Messages ===== */
.msg-row {
  padding: 20px 0;
  animation: fadeUp 250ms ease;
}
.msg-row:not(:last-child) { border-bottom: 1px solid var(--border-light); }
.msg-row.user { background: var(--bg-user-msg); }
.msg-row.assistant { background: var(--bg-ai-msg); }

.msg-inner {
  max-width: var(--chat-max);
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  gap: 16px;
}

.msg-avatar {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  font-size: 0.75rem;
  font-weight: 700;
}
.msg-row.user .msg-avatar {
  background: linear-gradient(135deg, #667eea, #764ba2);
  color: #fff;
}
.msg-row.assistant .msg-avatar {
  background: linear-gradient(135deg, var(--accent), #34d399);
  color: #fff;
}

.msg-content {
  flex: 1;
  min-width: 0;
  padding-top: 4px;
}

.msg-label {
  font-size: 0.78rem;
  font-weight: 600;
  margin-bottom: 6px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}
.msg-row.user .msg-label { color: #764ba2; }
.msg-row.assistant .msg-label { color: var(--accent); }

.msg-body {
  font-size: 0.94rem;
  line-height: 1.7;
  word-wrap: break-word;
}
.msg-body p { margin-bottom: 10px; }
.msg-body p:last-child { margin-bottom: 0; }
.msg-body ul, .msg-body ol { margin: 8px 0; padding-left: 24px; }
.msg-body li { margin-bottom: 4px; }
.msg-body strong { font-weight: 600; }
.msg-body a { color: var(--accent); text-decoration: underline; }

/* Code blocks */
.msg-body pre {
  background: var(--bg-code);
  color: var(--text-code);
  padding: 16px;
  border-radius: var(--radius-md);
  overflow-x: auto;
  margin: 12px 0;
  font-family: var(--font-mono);
  font-size: 0.84rem;
  line-height: 1.6;
  position: relative;
}
.msg-body code {
  font-family: var(--font-mono);
  font-size: 0.88em;
}
.msg-body :not(pre) > code {
  background: #f1f1f3;
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.85em;
}

.copy-code-btn {
  position: absolute;
  top: 8px;
  right: 8px;
  padding: 4px 10px;
  font-size: 0.72rem;
  color: #999;
  background: rgba(255,255,255,0.08);
  border-radius: 6px;
  opacity: 0;
  transition: opacity var(--transition), color var(--transition);
}
pre:hover .copy-code-btn { opacity: 1; }
.copy-code-btn:hover { color: #fff; background: rgba(255,255,255,0.15); }

/* Message actions */
.msg-actions {
  display: flex;
  gap: 4px;
  margin-top: 10px;
  opacity: 0;
  transition: opacity var(--transition);
}
.msg-row:hover .msg-actions { opacity: 1; }
.msg-action-btn {
  padding: 4px 8px;
  color: var(--text-secondary);
  border-radius: 6px;
  transition: all var(--transition);
  display: flex;
  align-items: center;
  gap: 4px;
  font-size: 0.75rem;
}
.msg-action-btn:hover { background: var(--border-light); color: var(--text-primary); }

/* Typing indicator */
.typing-indicator {
  display: flex;
  gap: 4px;
  padding: 4px 0;
}
.typing-indicator span {
  width: 6px;
  height: 6px;
  background: var(--accent);
  border-radius: 50%;
  animation: blink 1.2s infinite both;
}
.typing-indicator span:nth-child(2) { animation-delay: 0.2s; }
.typing-indicator span:nth-child(3) { animation-delay: 0.4s; }

/* Streaming cursor */
.streaming-cursor::after {
  content: '';
  display: inline-block;
  width: 2px;
  height: 1em;
  background: var(--accent);
  margin-left: 2px;
  animation: cursorBlink 0.8s infinite;
  vertical-align: text-bottom;
}

/* ===== Composer ===== */
.composer-wrapper {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border);
  padding: 16px 24px 20px;
}

.composer {
  max-width: var(--composer-max);
  margin: 0 auto;
}

.composer-inner {
  display: flex;
  align-items: flex-end;
  gap: 8px;
  background: var(--bg-composer-inner);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 8px 8px 8px 16px;
  transition: border-color var(--transition), box-shadow var(--transition);
}
.composer-inner:focus-within {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-glow);
}

.composer textarea {
  flex: 1;
  resize: none;
  border: none;
  background: transparent;
  padding: 8px 0;
  min-height: 24px;
  max-height: 200px;
  line-height: 1.5;
  font-size: 0.94rem;
  color: var(--text-primary);
}
.composer textarea::placeholder { color: var(--text-secondary); }

#sendBtn, #stopBtn {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: all var(--transition);
}

#sendBtn {
  background: var(--accent);
  color: var(--text-inverse);
}
#sendBtn:hover:not(:disabled) { background: var(--accent-hover); transform: scale(1.05); }
#sendBtn:disabled { opacity: 0.35; cursor: not-allowed; }

#stopBtn {
  background: var(--danger);
  color: var(--text-inverse);
}
#stopBtn:hover { opacity: 0.85; }

.disclaimer {
  text-align: center;
  font-size: 0.72rem;
  color: var(--text-secondary);
  margin-top: 8px;
  opacity: 0.7;
}

/* ===== Btn Icon ===== */
.btn-icon {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  color: var(--text-sidebar-muted);
  transition: all var(--transition);
}
.btn-icon:hover { background: var(--bg-sidebar-hover); color: var(--text-sidebar); }

/* ===== Overlay (mobile sidebar) ===== */
.overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  z-index: 90;
  backdrop-filter: blur(2px);
}

/* ===== Utility ===== */
.hidden { display: none !important; }

/* ===== Animations ===== */
@keyframes fadeUp {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes blink {
  0%, 80%, 100% { opacity: 0.3; transform: scale(0.8); }
  40% { opacity: 1; transform: scale(1); }
}
@keyframes cursorBlink {
  0%, 100% { opacity: 1; }
  50% { opacity: 0; }
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .sidebar {
    position: fixed;
    left: 0;
    top: 0;
    transform: translateX(-100%);
  }
  .sidebar.open { transform: translateX(0); }
  .overlay.show { display: block; }
  .topbar { display: flex; }

  .suggestions { grid-template-columns: 1fr; }
  .welcome { padding: 40px 20px; }
  .welcome h2 { font-size: 1.3rem; }

  .msg-inner { padding: 0 16px; }
  .composer-wrapper { padding: 12px 16px 16px; }
}

@media (min-width: 769px) {
  .topbar { display: none; }
}

/* ===== Scrollbar global ===== */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: #ddd; border-radius: 6px; }
::-webkit-scrollbar-thumb:hover { background: #bbb; }