/* ============================================================
   CSS CUSTOM PROPERTIES — LIGHT THEME (default)
   ============================================================ */
:root {
  --bg: #f4f7fb;
  --text: #1f2937;
  --card-bg: #ffffff;
  --card-shadow: 0 8px 24px rgba(0, 0, 0, 0.08);
  --subtitle-color: #4b5563;
  --border: #e5e7eb;
  --border-input: #d1d5db;
  --toolbar-btn-bg: #e5e7eb;
  --toolbar-btn-hover: #d1d5db;
  --user-bubble-bg: #2563eb;
  --user-bubble-text: #ffffff;
  --assistant-bubble-bg: #f9fafb;
  --assistant-bubble-text: #111827;
  --graph-label-bg: #f0f4ff;
  --graph-label-text: #1e40af;
  --graph-slider-label: #1e40af;
  --slider-value-text: #4b5563;
  --graph-sliders-bg: #f8fafc;
  --status-color: #2563eb;
  --login-bg: #f4f7fb;
  --login-card-bg: #ffffff;
  --btn-primary: #2563eb;
  --btn-primary-hover: #1d4ed8;
  --btn-primary-disabled: #93c5fd;
  --btn-secondary-bg: #e5e7eb;
  --btn-secondary-text: #111827;
  --btn-secondary-hover: #d1d5db;
  --icon-btn-hover: rgba(0, 0, 0, 0.06);
  --chip-bg: #eff6ff;
  --chip-text: #1d4ed8;
  --chip-border: #bfdbfe;
  --chip-hover: #dbeafe;
  --preview-bg: #f0f4ff;
  --preview-border: #bfdbfe;
  --textarea-bg: #ffffff;
  --textarea-text: #1f2937;
  --loading-bg: #f4f7fb;
  --typing-dot: #9ca3af;
}

/* ============================================================
   DARK THEME — via system preference (unless user forced light)
   ============================================================ */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #111827;
    --text: #f9fafb;
    --card-bg: #1f2937;
    --card-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
    --subtitle-color: #9ca3af;
    --border: #374151;
    --border-input: #4b5563;
    --toolbar-btn-bg: #374151;
    --toolbar-btn-hover: #4b5563;
    --user-bubble-bg: #3b82f6;
    --user-bubble-text: #ffffff;
    --assistant-bubble-bg: #374151;
    --assistant-bubble-text: #f9fafb;
    --graph-label-bg: #1e3a5f;
    --graph-label-text: #93c5fd;
    --graph-slider-label: #93c5fd;
    --slider-value-text: #9ca3af;
    --graph-sliders-bg: #1f2937;
    --status-color: #60a5fa;
    --login-bg: #111827;
    --login-card-bg: #1f2937;
    --btn-primary: #3b82f6;
    --btn-primary-hover: #2563eb;
    --btn-primary-disabled: #1d4ed8;
    --btn-secondary-bg: #374151;
    --btn-secondary-text: #f9fafb;
    --btn-secondary-hover: #4b5563;
    --icon-btn-hover: rgba(255, 255, 255, 0.08);
    --chip-bg: #1e3a5f;
    --chip-text: #93c5fd;
    --chip-border: #1d4ed8;
    --chip-hover: #1e40af;
    --preview-bg: #1e3a5f;
    --preview-border: #1d4ed8;
    --textarea-bg: #374151;
    --textarea-text: #f9fafb;
    --loading-bg: #111827;
    --typing-dot: #6b7280;
  }
}

/* ============================================================
   DARK THEME — manual override (user clicked the toggle)
   ============================================================ */
[data-theme="dark"] {
  --bg: #111827;
  --text: #f9fafb;
  --card-bg: #1f2937;
  --card-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
  --subtitle-color: #9ca3af;
  --border: #374151;
  --border-input: #4b5563;
  --toolbar-btn-bg: #374151;
  --toolbar-btn-hover: #4b5563;
  --user-bubble-bg: #3b82f6;
  --user-bubble-text: #ffffff;
  --assistant-bubble-bg: #374151;
  --assistant-bubble-text: #f9fafb;
  --graph-label-bg: #1e3a5f;
  --graph-label-text: #93c5fd;
  --graph-slider-label: #93c5fd;
  --slider-value-text: #9ca3af;
  --graph-sliders-bg: #1f2937;
  --status-color: #60a5fa;
  --login-bg: #111827;
  --login-card-bg: #1f2937;
  --btn-primary: #3b82f6;
  --btn-primary-hover: #2563eb;
  --btn-primary-disabled: #1d4ed8;
  --btn-secondary-bg: #374151;
  --btn-secondary-text: #f9fafb;
  --btn-secondary-hover: #4b5563;
  --icon-btn-hover: rgba(255, 255, 255, 0.08);
  --chip-bg: #1e3a5f;
  --chip-text: #93c5fd;
  --chip-border: #1d4ed8;
  --chip-hover: #1e40af;
  --preview-bg: #1e3a5f;
  --preview-border: #1d4ed8;
  --textarea-bg: #374151;
  --textarea-text: #f9fafb;
  --loading-bg: #111827;
  --typing-dot: #6b7280;
}

/* ============================================================
   BASE
   ============================================================ */
* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  transition: background 0.2s, color 0.2s;
}

/* ============================================================
   LOADING OVERLAY
   ============================================================ */
.loading-overlay {
  position: fixed;
  inset: 0;
  background: var(--loading-bg);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  z-index: 2000;
  gap: 16px;
}

.loading-spinner {
  width: 44px;
  height: 44px;
  border: 4px solid var(--border);
  border-top-color: var(--btn-primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

.loading-text {
  color: var(--subtitle-color);
  font-size: 1rem;
  margin: 0;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* ============================================================
   LAYOUT
   ============================================================ */
.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 32px 16px;
}

/* ============================================================
   HEADER
   ============================================================ */
.header {
  text-align: center;
  margin-bottom: 24px;
}

.header-top {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  margin-bottom: 8px;
}

.header-top h1 {
  margin: 0;
  font-size: 2rem;
}

.subtitle {
  margin: 0 auto;
  max-width: 700px;
  color: var(--subtitle-color);
  line-height: 1.5;
}

/* ============================================================
   ICON BUTTON (dark-mode toggle, etc.)
   ============================================================ */
.icon-button {
  background: transparent;
  border: none;
  border-radius: 8px;
  padding: 6px 8px;
  font-size: 1.25rem;
  cursor: pointer;
  line-height: 1;
  transition: background 0.15s;
  flex-shrink: 0;
}

.icon-button:hover {
  background: var(--icon-btn-hover);
}

/* ============================================================
   CARD
   ============================================================ */
.card {
  background: var(--card-bg);
  border-radius: 16px;
  padding: 24px;
  box-shadow: var(--card-shadow);
  transition: background 0.2s, box-shadow 0.2s;
}

/* ============================================================
   CHAT
   ============================================================ */
.chat {
  display: flex;
  flex-direction: column;
  gap: 14px;
  min-height: 320px;
  max-height: 700px;
  overflow-y: auto;
  padding: 8px 4px 16px 4px;
  margin-bottom: 20px;
}

.message {
  display: flex;
}

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

.message.assistant {
  justify-content: flex-start;
}

.message-bubble {
  max-width: 80%;
  padding: 14px 16px;
  border-radius: 16px;
  line-height: 1.6;
  white-space: pre-wrap;
  overflow-wrap: break-word;
  border: 1px solid var(--border);
  transition: background 0.2s, color 0.2s, border-color 0.2s;
}

.message.user .message-bubble {
  background: var(--user-bubble-bg);
  color: var(--user-bubble-text);
  border-bottom-right-radius: 6px;
  border: none;
}

.message.assistant .message-bubble {
  background: var(--assistant-bubble-bg);
  color: var(--assistant-bubble-text);
  border-bottom-left-radius: 6px;
}

/* Image in a chat bubble (uploaded by user) */
.chat-image {
  display: block;
  max-width: 100%;
  max-height: 300px;
  border-radius: 8px;
  margin-bottom: 8px;
  object-fit: contain;
}

/* ============================================================
   TYPING INDICATOR (shown during streaming)
   ============================================================ */
.typing-indicator {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 2px 0;
}

.typing-indicator span {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--typing-dot);
  display: inline-block;
  animation: bounce 1.2s ease-in-out infinite;
}

.typing-indicator span:nth-child(2) {
  animation-delay: 0.2s;
}

.typing-indicator span:nth-child(3) {
  animation-delay: 0.4s;
}

@keyframes bounce {
  0%, 60%, 100% { transform: translateY(0); }
  30% { transform: translateY(-6px); }
}

/* ============================================================
   SUGGESTION CHIPS
   ============================================================ */
.suggestion-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  padding: 4px 0 8px 0;
}

.suggestion-chip {
  background: var(--chip-bg);
  color: var(--chip-text);
  border: 1px solid var(--chip-border);
  border-radius: 20px;
  padding: 7px 14px;
  font-size: 0.875rem;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s;
  line-height: 1.4;
}

.suggestion-chip:hover {
  background: var(--chip-hover);
}

/* ============================================================
   CHAT FORM
   ============================================================ */
.chat-form {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.label {
  font-weight: 600;
}

/* ============================================================
   MATH TOOLBAR
   ============================================================ */
.math-toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-bottom: 8px;
}

.math-toolbar button {
  padding: 6px 10px;
  border-radius: 8px;
  background: var(--toolbar-btn-bg);
  border: 1px solid var(--border-input);
  font-size: 0.9rem;
  cursor: pointer;
  color: var(--text);
  transition: background 0.15s;
}

.math-toolbar button:hover {
  background: var(--toolbar-btn-hover);
}

/* Upload button inside toolbar (slightly differentiated) */
.upload-btn {
  margin-left: auto;
}

/* ============================================================
   TEXTAREA
   ============================================================ */
.textarea {
  width: 100%;
  resize: vertical;
  padding: 14px;
  font-size: 1rem;
  border: 1px solid var(--border-input);
  border-radius: 10px;
  min-height: 60px;
  max-height: 200px;
  overflow-y: auto;
  background: var(--textarea-bg);
  color: var(--textarea-text);
  transition: border-color 0.15s, background 0.2s, color 0.2s;
}

.textarea:focus {
  outline: none;
  border-color: var(--btn-primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

/* Drag-and-drop highlight */
.textarea.drag-over {
  border-color: var(--btn-primary);
  background: var(--chip-bg);
}

/* ============================================================
   IMAGE PREVIEW
   ============================================================ */
.image-preview-container {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  padding: 8px 10px;
  background: var(--preview-bg);
  border: 1px solid var(--preview-border);
  border-radius: 10px;
}

.image-preview-thumb {
  max-width: 120px;
  max-height: 90px;
  border-radius: 6px;
  object-fit: contain;
  border: 1px solid var(--border);
}

.remove-image-btn {
  background: transparent;
  border: 1px solid var(--border-input);
  border-radius: 50%;
  width: 24px;
  height: 24px;
  font-size: 0.75rem;
  cursor: pointer;
  color: var(--text);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: background 0.15s;
}

.remove-image-btn:hover {
  background: var(--toolbar-btn-hover);
}

/* ============================================================
   BUTTON ROW
   ============================================================ */
.button-row {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.button {
  background: var(--btn-primary);
  color: white;
  border: none;
  border-radius: 10px;
  padding: 12px 20px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s;
}

.button:hover {
  background: var(--btn-primary-hover);
}

.button:disabled {
  background: var(--btn-primary-disabled);
  cursor: not-allowed;
}

.button.secondary {
  background: var(--btn-secondary-bg);
  color: var(--btn-secondary-text);
}

.button.secondary:hover {
  background: var(--btn-secondary-hover);
}

.button.secondary:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* ============================================================
   STATUS
   ============================================================ */
.status {
  min-height: 24px;
  margin-top: 14px;
  font-weight: 600;
  color: var(--status-color);
}

.error {
  color: #b91c1c;
}

/* ============================================================
   GRAPH CONTAINERS
   ============================================================ */
.graph-container {
  margin: 12px 0;
  border-radius: 10px;
  overflow: hidden;
  border: 1px solid var(--border);
  background: var(--card-bg);
}

.graph-container svg {
  display: block;
}

.graph-container text {
  font-family: Arial, sans-serif;
  font-size: 12px;
}

.graph-label {
  padding: 6px 12px;
  background: var(--graph-label-bg);
  font-family: monospace;
  font-size: 0.85rem;
  color: var(--graph-label-text);
  border-bottom: 1px solid var(--border);
}

.message-bubble.has-graph {
  max-width: 90%;
  white-space: normal;
}

.graph-sliders {
  padding: 8px 12px;
  background: var(--graph-sliders-bg);
  border-top: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.graph-slider-row {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.85rem;
}

.graph-slider-row label {
  font-weight: 600;
  min-width: 24px;
  color: var(--graph-slider-label);
}

.graph-slider-row input[type="range"] {
  flex: 1;
  cursor: pointer;
  accent-color: var(--btn-primary);
}

.graph-slider-row .slider-value {
  min-width: 40px;
  text-align: right;
  font-family: monospace;
  color: var(--slider-value-text);
}

.graph-error {
  padding: 12px;
  color: #b91c1c;
  font-style: italic;
  font-size: 0.9rem;
}

/* ============================================================
   TRIANGLE DIAGRAM CONTAINERS
   ============================================================ */
.triangle-container {
  display: inline-block;
  margin: 12px 0;
  border-radius: 10px;
  overflow: hidden;
  border: 1px solid var(--border);
  background: var(--card-bg);
  padding: 8px;
}

.triangle-svg {
  display: block;
  overflow: visible;
}

.shape-svg {
  display: block;
  overflow: visible;
}


.login-overlay {
  position: fixed;
  inset: 0;
  background: var(--login-bg);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  transition: background 0.2s;
}

.login-card {
  background: var(--login-card-bg);
  border-radius: 16px;
  padding: 40px 32px;
  box-shadow: var(--card-shadow);
  text-align: center;
  max-width: 400px;
  width: 90%;
  transition: background 0.2s;
}

.login-card h1 {
  margin-bottom: 8px;
  font-size: 2rem;
}

.login-subtitle {
  color: var(--subtitle-color);
  margin-bottom: 24px;
  line-height: 1.5;
}

.login-form {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.login-input {
  width: 100%;
  padding: 14px;
  font-size: 1rem;
  border: 1px solid var(--border-input);
  border-radius: 10px;
  text-align: center;
  background: var(--textarea-bg);
  color: var(--textarea-text);
  transition: background 0.2s, color 0.2s;
}

.login-input:focus {
  outline: none;
  border-color: var(--btn-primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.login-button {
  width: 100%;
}

.login-error {
  color: #b91c1c;
  font-weight: 600;
  min-height: 20px;
  font-size: 0.9rem;
}

/* ============================================================
   SUBSCRIPT TOGGLE ACTIVE STATE
   ============================================================ */
#subscript-toggle.active {
  background: var(--btn-primary);
  color: white;
  border-color: var(--btn-primary);
}

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width: 640px) {
  .card {
    padding: 18px;
  }

  .message-bubble {
    max-width: 92%;
  }

  .button {
    width: 100%;
  }

  .header-top h1 {
    font-size: 1.5rem;
  }
}