/* Lychee AI - ChatGPT-Style Conversational UI Styles */
:root {
  --primary: #c82333;
  --primary-hover: #b01e2c;
  --primary-light: #fff5f5;
  --primary-border: #ffc9c9;
  --accent: #e03131;
  --text-main: #1f2937;
  --text-muted: #6b7280;
  --text-light: #9ca3af;
  --bg-page: #ffffff;
  --bg-sidebar: #f9fafb;
  --bg-card: #ffffff;
  --bg-subtle: #f3f4f6;
  --bg-user-bubble: #f3f4f6;
  --bg-assistant-bubble: #ffffff;
  --border-color: #e5e7eb;
  --border-focus: #c82333;
  --success: #16a34a;
  --success-bg: #f0fdf4;
  --warning: #d97706;
  --warning-bg: #fffbeb;
  --danger: #dc2626;
  --danger-bg: #fef2f2;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --font-hanzi: 'Noto Sans SC', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 20px;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.04);
  --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.08);
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-page);
  color: var(--text-main);
  line-height: 1.6;
  height: 100vh;
  display: flex;
  overflow: hidden;
  -webkit-font-smoothing: antialiased;
}

/* App Shell */
.app-layout {
  display: flex;
  width: 100%;
  max-width: 100vw;
  height: 100vh;
  position: relative;
  overflow: hidden;
}

/* Sidebar */
.sidebar {
  width: 260px;
  background-color: var(--bg-sidebar);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  padding: 0.85rem;
  flex-shrink: 0;
  transition: transform 0.25s ease;
  z-index: 50;
}

.sidebar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 0.85rem;
}

.brand-wrap {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  text-decoration: none;
  color: var(--text-main);
}

.brand-logo-img {
  width: 38px;
  height: 38px;
  object-fit: contain;
  border-radius: 8px;
  display: block;
  flex-shrink: 0;
}

.brand-title {
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.btn-new-chat {
  display: flex;
  align-items: center;
  justify-content: flex-start;
  gap: 0.5rem;
  width: 100%;
  padding: 0.65rem 0.85rem;
  background: #ffffff;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  color: var(--text-main);
  font-weight: 600;
  font-size: 0.9rem;
  cursor: pointer;
  box-shadow: var(--shadow-sm);
  transition: all 0.15s ease;
}

.btn-new-chat:hover {
  background: var(--bg-subtle);
  border-color: #d1d5db;
}

.history-section {
  flex: 1;
  overflow-y: auto;
  margin-top: 1rem;
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.history-title {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--text-light);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.25rem 0.5rem;
}

.history-item {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.55rem 0.75rem;
  border-radius: var(--radius-sm);
  color: var(--text-main);
  font-size: 0.85rem;
  text-decoration: none;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  cursor: pointer;
}

.history-item:hover, .history-item.active {
  background: var(--bg-subtle);
}

.history-item.active {
  font-weight: 600;
  color: var(--primary);
}

.sidebar-footer {
  border-top: 1px solid var(--border-color);
  padding-top: 0.75rem;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

/* Chat Main Area */
.chat-main {
  flex: 1;
  display: flex;
  flex-direction: column;
  height: 100vh;
  position: relative;
  background: var(--bg-page);
  min-width: 0;
}

/* Top Bar */
.chat-topbar {
  height: 56px;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.25rem;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(8px);
  z-index: 20;
}

.topbar-left {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.btn-menu-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  color: var(--text-main);
}

/* Mode Selector Dropdown */
.mode-selector-wrap {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  background: var(--bg-subtle);
  padding: 0.3rem 0.6rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
}

.mode-label {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-muted);
}

.mode-select {
  border: none;
  background: transparent;
  font-family: inherit;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--primary);
  cursor: pointer;
  outline: none;
}

.topbar-right {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.quota-indicator {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-main);
  background: var(--bg-subtle);
  padding: 0.35rem 0.75rem;
  border-radius: 20px;
  border: 1px solid var(--border-color);
  cursor: pointer;
  transition: all 0.15s ease;
}

.quota-indicator:hover {
  background: #ffffff;
  border-color: var(--primary);
}

.quota-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--success);
}

.quota-bar-wrap {
  width: 48px;
  height: 6px;
  background: #e5e7eb;
  border-radius: 3px;
  overflow: hidden;
  display: inline-block;
}

.quota-bar-fill {
  height: 100%;
  background: var(--primary);
  border-radius: 3px;
  transition: width 0.3s ease;
}

/* Message Stream */
.messages-container {
  flex: 1;
  overflow-y: auto;
  padding: 1.5rem 1rem 8rem 1rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  scroll-behavior: smooth;
}

.messages-inner {
  width: 100%;
  max-width: 780px;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

/* Empty State / Welcome Screen */
.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 4rem 1rem 2rem 1rem;
  text-align: center;
}

.empty-title {
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 0.5rem;
}

.empty-desc {
  font-size: 0.95rem;
  color: var(--text-muted);
  margin-bottom: 2rem;
  max-width: 500px;
}

.prompt-chips-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 0.75rem;
  width: 100%;
  max-width: 720px;
}

.prompt-chip {
  background: #ffffff;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1rem;
  text-align: left;
  cursor: pointer;
  transition: all 0.15s ease;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}

.prompt-chip:hover {
  border-color: var(--primary);
  background: var(--primary-light);
  transform: translateY(-2px);
}

.prompt-chip strong {
  font-size: 0.9rem;
  color: var(--text-main);
}

.prompt-chip span {
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* Message Row */
.message-row {
  display: flex;
  gap: 0.85rem;
  width: 100%;
}

.message-row.user {
  justify-content: flex-end;
}

.message-avatar {
  width: 32px;
  height: 32px;
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 0.95rem;
  flex-shrink: 0;
}

.message-avatar.assistant {
  background: transparent;
  padding: 0;
  overflow: hidden;
}

.message-avatar-img {
  width: 30px;
  height: 30px;
  object-fit: contain;
  border-radius: 6px;
  display: block;
}

.message-avatar.user {
  background: #4b5563;
  color: #fff;
}

.message-body {
  max-width: 85%;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.message-row.user .message-bubble {
  background: var(--bg-user-bubble);
  border: 1px solid #e5e7eb;
  border-radius: 18px 18px 4px 18px;
  padding: 0.75rem 1.15rem;
  font-size: 0.95rem;
  color: var(--text-main);
}

.message-row.assistant .message-bubble {
  background: transparent;
  font-size: 0.95rem;
  color: var(--text-main);
  line-height: 1.65;
}

.message-mode-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-muted);
  margin-bottom: 0.25rem;
}

/* Modular Learning Cards inside Messages */
.inline-card {
  background: #ffffff;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.15rem;
  margin-top: 0.75rem;
  box-shadow: var(--shadow-sm);
}

/* Vocab Card */
.vocab-card {
  border-left: 4px solid var(--primary);
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.vocab-card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.vocab-hanzi {
  font-size: 1.8rem;
  font-family: var(--font-hanzi);
  font-weight: 700;
  color: var(--text-main);
}

.vocab-pinyin {
  font-size: 1rem;
  font-weight: 500;
  color: var(--primary);
}

.vocab-meaning {
  font-size: 0.9rem;
  color: var(--text-muted);
}

/* Correction Diff Card */
.correction-diff-card {
  border-left: 4px solid var(--warning);
  background: #fffdfa;
}

.diff-original {
  color: var(--danger);
  text-decoration: line-through;
  font-family: var(--font-hanzi);
  margin-bottom: 0.3rem;
}

.diff-corrected {
  color: var(--success);
  font-weight: 600;
  font-family: var(--font-hanzi);
  font-size: 1.05rem;
}

.diff-explanation {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-top: 0.4rem;
}

/* Audio Button */
.audio-play-btn {
  background: var(--bg-subtle);
  border: 1px solid var(--border-color);
  border-radius: 20px;
  padding: 0.3rem 0.75rem;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.15s;
}

.audio-play-btn:hover {
  background: var(--primary-light);
  color: var(--primary);
  border-color: var(--primary-border);
}

/* Floating Bottom Composer */
.chat-composer-wrap {
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  padding: 1rem 1.25rem;
  background: linear-gradient(180deg, rgba(255,255,255,0) 0%, rgba(255,255,255,1) 35%);
  display: flex;
  justify-content: center;
  z-index: 30;
}

.composer-box {
  width: 100%;
  max-width: 780px;
  background: #ffffff;
  border: 1px solid #d1d5db;
  border-radius: 24px;
  box-shadow: 0 4px 16px rgba(0,0,0,0.06);
  display: flex;
  flex-direction: column;
  padding: 0.65rem 0.85rem 0.5rem 1rem;
  transition: border-color 0.15s, box-shadow 0.15s;
}

.composer-box:focus-within {
  border-color: var(--primary);
  box-shadow: 0 4px 20px rgba(200,35,51,0.12);
}

.composer-textarea {
  width: 100%;
  border: none;
  outline: none;
  font-family: inherit;
  font-size: 0.95rem;
  line-height: 1.5;
  resize: none;
  max-height: 160px;
  min-height: 24px;
  background: transparent;
}

.composer-bottom {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 0.35rem;
}

.composer-hints {
  font-size: 0.75rem;
  color: var(--text-light);
}

.composer-actions {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.btn-send {
  width: 34px;
  height: 34px;
  border-radius: 50%;
  background: var(--primary);
  color: #fff;
  border: none;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.15s;
}

.btn-send:hover:not(:disabled) {
  background: var(--primary-hover);
  transform: scale(1.05);
}

.btn-send:disabled {
  background: #e5e7eb;
  color: #9ca3af;
  cursor: not-allowed;
}

.btn-stop {
  display: none;
  padding: 0.3rem 0.75rem;
  background: #ffffff;
  border: 1px solid var(--border-color);
  border-radius: 20px;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-muted);
  cursor: pointer;
}

.btn-stop:hover {
  background: var(--bg-subtle);
}

/* Modal Backdrop & Dialog */
.modal-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
}

.modal-dialog {
  background: #fff;
  border-radius: var(--radius-md);
  padding: 1.75rem;
  max-width: 520px;
  width: 90%;
  max-height: 90vh;
  overflow-y: auto;
  box-shadow: var(--shadow-lg);
}

/* Mobile Responsive */
@media (max-width: 768px) {
  .sidebar {
    position: fixed;
    top: 0;
    bottom: 0;
    left: -290px;
    width: 280px;
    height: 100vh;
    background-color: #ffffff;
    box-shadow: 4px 0 25px rgba(0, 0, 0, 0.2);
    z-index: 100;
    transition: left 0.25s cubic-bezier(0.16, 1, 0.3, 1);
    transform: none;
  }
  .sidebar.open {
    left: 0;
    transform: none;
  }
  .sidebar-backdrop {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.45);
    z-index: 99;
  }
  .sidebar-backdrop.active {
    display: block;
  }
  .chat-topbar {
    padding: 0 0.75rem;
  }
  .topbar-right #btn-upgrade-top {
    display: none;
  }
  .quota-indicator {
    padding: 0.25rem 0.5rem;
    font-size: 0.75rem;
  }
  .btn-menu-toggle {
    display: block;
  }
  .prompt-chips-grid {
    grid-template-columns: 1fr;
  }
  .chat-composer-wrap {
    padding: 0.6rem 0.75rem;
  }
  .messages-container {
    padding: 1rem 0.75rem 8rem 0.75rem;
  }
}