/* ─── Student Hub Premium Stylesheet ─── */

/* Global Reset & Container */
.student-hub-page {
  background-color: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  height: 100vh;
  overflow: hidden;
  transition: background-color var(--transition-smooth), color var(--transition-smooth);
}

/* Custom Scrollbars */
.options-panel::-webkit-scrollbar,
.output-workspace::-webkit-scrollbar,
.dropdown-list::-webkit-scrollbar,
.timeline-task-list::-webkit-scrollbar,
.flashcard-back-content::-webkit-scrollbar {
  width: 6px;
  height: 6px;
}

.options-panel::-webkit-scrollbar-track,
.output-workspace::-webkit-scrollbar-track,
.dropdown-list::-webkit-scrollbar-track,
.flashcard-back-content::-webkit-scrollbar-track {
  background: transparent;
}

.options-panel::-webkit-scrollbar-thumb,
.output-workspace::-webkit-scrollbar-thumb,
.dropdown-list::-webkit-scrollbar-thumb,
.flashcard-back-content::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 10px;
}

.options-panel::-webkit-scrollbar-thumb:hover,
.output-workspace::-webkit-scrollbar-thumb:hover,
.dropdown-list::-webkit-scrollbar-thumb:hover {
  background: var(--text-muted);
}

/* --- API Warning Banner --- */
.api-warning-banner {
  background-color: var(--danger);
  color: #fff;
  padding: 8px 16px;
  text-align: center;
  font-size: 13px;
  font-weight: 500;
  width: 100%;
  z-index: 1000;
  box-shadow: var(--shadow-sm);
  animation: slideDown 0.3s ease;
}

/* --- Header Layout --- */
.hub-header {
  height: var(--header-height);
  background-color: rgba(var(--surface-rgb), 0.75);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 20px;
  flex-shrink: 0;
  z-index: 1100;
}

.hub-header .header-left {
  display: flex;
  align-items: center;
  gap: 12px;
}

.hub-header .back-btn {
  border-radius: 50%;
  padding: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.hub-header .header-brand {
  display: flex;
  align-items: center;
  gap: 10px;
}

.hub-header .brand-h1 {
  font-size: 16px;
  font-weight: 600;
  margin: 0;
  letter-spacing: -0.3px;
}

.hub-header .brand-accent {
  color: var(--primary);
}

.hub-header .tabs-navigation {
  display: flex;
  background-color: rgba(var(--surface-2-rgb), 0.5);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 3px;
  gap: 2px;
}

.hub-header .tab-btn {
  background: none;
  border: none;
  color: var(--text-dim);
  font-family: var(--font-sans);
  font-size: 13px;
  font-weight: 500;
  padding: 6px 16px;
  border-radius: var(--radius);
  cursor: pointer;
  transition: all var(--transition-smooth);
}

.hub-header .tab-btn:hover {
  color: var(--text);
}

.hub-header .tab-btn.active {
  background-color: var(--surface-3);
  color: var(--text);
  box-shadow: var(--shadow-sm);
}

/* --- Floating Context-Aware History Dropdown --- */
.history-dropdown-container {
  position: relative;
  display: inline-block;
}

.history-dropdown {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  width: 320px;
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  z-index: 10000;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  animation: dropdownFadeIn 0.25s cubic-bezier(0.16, 1, 0.3, 1) both;
}

.history-dropdown.hidden {
  display: none;
}

.dropdown-header {
  padding: 12px 16px;
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  color: var(--text-dim);
  border-bottom: 1px solid var(--border);
  background-color: var(--surface-2);
}

.dropdown-list {
  max-height: 280px;
  overflow-y: auto;
  padding: 8px;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.decks-empty {
  font-size: 12px;
  color: var(--text-muted);
  font-style: italic;
  padding: 12px;
  text-align: center;
  margin: 0;
}

.deck-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background-color: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 8px 12px;
  cursor: pointer;
  transition: all var(--transition-smooth);
  gap: 8px;
}

.deck-item:hover {
  border-color: var(--primary);
  background-color: var(--surface-hover);
}

.deck-item.active {
  border-color: var(--primary);
  background-color: var(--primary-glow);
}

.deck-info {
  display: flex;
  align-items: center;
  gap: 8px;
  min-width: 0;
  flex-grow: 1;
}

.deck-icon {
  font-size: 16px;
  flex-shrink: 0;
}

.deck-details {
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.deck-name {
  font-size: 12px;
  font-weight: 600;
  color: var(--text);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.deck-meta {
  font-size: 10px;
  color: var(--text-muted);
}

.deck-delete-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  padding: 4px;
  border-radius: 4px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-fast);
}

.deck-delete-btn:hover {
  color: var(--danger);
  background-color: rgba(229, 83, 75, 0.1);
}

.deck-delete-btn svg {
  width: 14px;
  height: 14px;
}

@keyframes dropdownFadeIn {
  from {
    opacity: 0;
    transform: translateY(6px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* --- Theme Color Adaptability indicators --- */
html[data-theme="amoled-dark"] { --calendar-invert: 0.9; }
html[data-theme="corporate-gray"] { --calendar-invert: 0.8; }
html[data-theme="nature-green"] { --calendar-invert: 0.2; }
html[data-theme="professional-light"] { --calendar-invert: 0.1; }
html[data-theme="minimal-white"] { --calendar-invert: 0.1; }
:root { --calendar-invert: 0.9; }

/* --- Main Layout --- */
.hub-main-content {
  flex-grow: 1;
  overflow: hidden;
  position: relative;
  display: flex;
  flex-direction: column;
}

.hub-view {
  display: none;
  height: 100%;
  width: 100%;
}

.hub-view.active {
  display: flex;
  flex-direction: column;
  flex-grow: 1;
  height: 100%;
}

.split-layout {
  display: flex;
  height: 100%;
  width: 100%;
  flex-grow: 1;
}

/* --- Options Panel Layout --- */
.options-panel {
  width: 320px;
  background-color: rgba(var(--surface-2-rgb), 0.65);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-right: 1px solid var(--border);
  padding: 24px;
  overflow-y: auto;
  flex-shrink: 0;
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.panel-heading {
  font-size: 18px;
  font-weight: 700;
  margin: 0;
  letter-spacing: -0.4px;
}

.panel-subtext {
  font-size: 12px;
  color: var(--text-dim);
  line-height: 1.6;
  margin: 0;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.form-group label {
  font-size: 11px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-dim);
}

/* --- Output Workspace --- */
.output-workspace {
  flex-grow: 1;
  padding: 32px;
  overflow-y: auto;
  background-color: transparent;
  display: flex;
  flex-direction: column;
  gap: 24px;
}

/* --- Study Progress Header --- */
.workspace-header {
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 16px 20px;
  display: flex;
  flex-direction: column;
  gap: 10px;
  animation: fadeIn 0.4s ease both;
  box-shadow: var(--shadow-sm);
}

.progress-info {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.progress-title {
  font-size: 13px;
  font-weight: 600;
  color: var(--text-dim);
}

.progress-value {
  font-size: 13px;
  font-weight: 700;
  color: var(--success);
}

.progress-track {
  height: 6px;
  background-color: var(--surface-3);
  border-radius: 10px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--primary-light));
  border-radius: 10px;
  transition: width 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

/* --- Placeholders --- */
.workspace-placeholder {
  margin: auto;
  text-align: center;
  max-width: 400px;
  padding: 40px 20px;
  animation: fadeIn 0.5s ease both;
}

.placeholder-icon {
  font-size: 54px;
  margin-bottom: 20px;
  filter: drop-shadow(0 8px 16px rgba(0,0,0,0.15));
  animation: float 4s ease-in-out infinite;
}

.workspace-placeholder h3 {
  font-size: 20px;
  font-weight: 700;
  margin: 0 0 10px 0;
  letter-spacing: -0.3px;
}

.workspace-placeholder p {
  font-size: 13px;
  color: var(--text-dim);
  line-height: 1.6;
  margin: 0;
}

/* --- Input Fields Polish --- */
.form-textarea {
  width: 100%;
  height: 120px;
  padding: 12px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background-color: var(--surface);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: 13px;
  resize: vertical;
  outline: none;
  box-sizing: border-box;
  transition: border-color var(--transition-smooth), box-shadow var(--transition-smooth);
}

.form-textarea:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-glow);
}

.form-input {
  width: 100%;
  padding: 10px 12px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background-color: var(--surface);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: 13px;
  outline: none;
  box-sizing: border-box;
  transition: border-color var(--transition-smooth), box-shadow var(--transition-smooth);
}

.form-input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-glow);
}

/* Customized Date Picker input */
.date-input-container {
  position: relative;
  display: flex;
  align-items: center;
  width: 100%;
}

.date-input-container .calendar-icon {
  position: absolute;
  left: 12px;
  width: 16px;
  height: 16px;
  color: var(--text-dim);
  pointer-events: none;
  z-index: 5;
}

.date-input-container .form-input {
  padding-left: 36px;
}

.date-input-container .form-input[type="date"]::-webkit-calendar-picker-indicator {
  cursor: pointer;
  filter: invert(var(--calendar-invert)) hue-rotate(180deg) brightness(1.2);
  opacity: 0.6;
  transition: opacity var(--transition-fast);
}

.date-input-container .form-input[type="date"]::-webkit-calendar-picker-indicator:hover {
  opacity: 1;
}

/* File upload dropzones */
.upload-dropzone {
  border: 2px dashed var(--border);
  border-radius: var(--radius-lg);
  padding: 20px;
  text-align: center;
  background-color: var(--surface);
  cursor: pointer;
  position: relative;
  transition: all var(--transition-smooth);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
}

.upload-dropzone:hover {
  border-color: var(--primary);
  background-color: var(--surface-hover);
}

.upload-dropzone.dragover {
  border-color: var(--success);
  background-color: var(--primary-glow);
  transform: scale(1.02);
}

.upload-icon {
  width: 28px;
  height: 28px;
  color: var(--text-dim);
  transition: transform var(--transition-smooth);
}

.upload-dropzone:hover .upload-icon {
  transform: translateY(-2px);
}

.upload-text {
  font-size: 12px;
  color: var(--text-dim);
}

.upload-filename {
  font-size: 12px;
  font-weight: 600;
  color: var(--primary);
  word-break: break-all;
}

.file-input {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  opacity: 0;
  cursor: pointer;
}

/* Buttons */
.btn.primary {
  background: linear-gradient(135deg, var(--primary), var(--primary-strong));
  border: none;
  color: #ffffff !important;
  font-weight: 600;
  font-size: 13px;
  padding: 12px;
  border-radius: var(--radius-lg);
  box-shadow: 0 4px 12px var(--primary-glow);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  transition: all var(--transition-smooth);
}

.btn.primary:hover {
  transform: translateY(-1.5px);
  box-shadow: 0 6px 16px var(--primary-glow);
  filter: brightness(1.1);
}

.btn.primary:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

.ai-spinner {
  width: 14px;
  height: 14px;
  border: 2px solid rgba(255, 255, 255, 0.3);
  border-top-color: #ffffff;
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  display: inline-block;
}

/* --- Flashcards Workspace Grid --- */
.flashcards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 24px;
  animation: fadeIn 0.4s ease both;
}

/* --- 3D Flippable Flashcard Layout --- */
.flashcard {
  perspective: 1200px;
  height: 190px;
  cursor: pointer;
  position: relative;
}

.flashcard-inner {
  position: relative;
  width: 100%;
  height: 100%;
  text-align: center;
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
  transform-style: preserve-3d;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
}

.flashcard.flipped .flashcard-inner {
  transform: rotateY(180deg);
}

.flashcard:hover {
  transform: translateY(-4px);
  transition: transform var(--transition-smooth);
}

.flashcard-front,
.flashcard-back {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
  border-radius: var(--radius-lg);
  padding: 20px;
  box-sizing: border-box;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  overflow: hidden;
}

.flashcard-front {
  background-color: var(--surface);
  color: var(--text);
  border: 1px solid var(--border);
  border-top: 4px solid var(--card-color, var(--primary));
  font-weight: 600;
  font-size: 14px;
  line-height: 1.6;
  transition: opacity 0.3s ease, filter 0.3s ease;
}

.flashcard-back {
  background: var(--card-gradient, linear-gradient(135deg, var(--primary), var(--primary-light)));
  color: #ffffff !important;
  transform: rotateY(180deg);
  font-size: 13px;
  line-height: 1.6;
  border: none;
  font-weight: 400;
  text-align: left;
}

.flashcard-back-content {
  flex-grow: 1;
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 100%;
  overflow-y: auto;
  padding-right: 4px;
  margin-bottom: 6px;
}

.flashcard-back-answer {
  font-size: 12.5px;
  line-height: 1.5;
  margin: 0;
  color: #ffffff;
}

.flashcard-back-answer strong {
  font-weight: 700;
  text-shadow: 0 0 1px rgba(255,255,255,0.4);
}

/* Category & index badge elements on front */
.flashcard-category-badge {
  position: absolute;
  top: 10px;
  left: 12px;
  font-size: 9px;
  font-weight: 700;
  text-transform: uppercase;
  background-color: var(--surface-3);
  border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 2px 8px;
  border-radius: 20px;
  letter-spacing: 0.5px;
}

.flashcard-index-label {
  position: absolute;
  top: 10px;
  right: 12px;
  font-size: 10px;
  font-weight: 600;
  color: var(--text-muted);
}

.flashcard-front p {
  font-size: 14px;
  font-weight: 600;
  line-height: 1.5;
  margin: 0;
  text-align: center;
  max-width: 90%;
}

/* Mnemonic Aid box styling */
.card-mnemonic-box {
  background-color: rgba(0, 0, 0, 0.18);
  border-left: 3px solid rgba(255, 255, 255, 0.6);
  border-radius: 4px;
  padding: 8px 10px;
  font-size: 11px;
  line-height: 1.4;
  color: rgba(255, 255, 255, 0.95);
  margin-top: 4px;
}

.card-mnemonic-box strong {
  font-weight: 700;
}

/* Mastery status styles */
.flashcard.mastered .flashcard-front {
  opacity: 0.65;
  filter: grayscale(30%);
  box-shadow: 0 0 12px rgba(63, 185, 80, 0.15);
}

.flashcard-mastered-badge {
  position: absolute;
  top: 36px;
  right: 12px;
  background-color: var(--success);
  color: #fff;
  font-size: 9px;
  font-weight: 700;
  text-transform: uppercase;
  padding: 2px 6px;
  border-radius: 10px;
  display: flex;
  align-items: center;
  gap: 2px;
  letter-spacing: 0.3px;
}

.card-mastery-btn {
  background-color: rgba(255, 255, 255, 0.25);
  border: none;
  color: #fff;
  border-radius: var(--radius);
  padding: 6px 12px;
  font-size: 11px;
  font-weight: 700;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 4px;
  transition: all var(--transition-fast);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  width: 100%;
}

.card-mastery-btn:hover {
  background-color: rgba(255, 255, 255, 0.4);
}

.card-mastery-btn.active {
  background-color: #ffffff;
  color: var(--success);
}

.flashcard-appear {
  animation: cardAppear 0.4s cubic-bezier(0.16, 1, 0.3, 1) both;
}

/* --- Schedule Timeline --- */
.schedule-timeline {
  display: flex;
  flex-direction: column;
  gap: 24px;
  max-width: 750px;
  margin: 0 auto;
  width: 100%;
  position: relative;
  padding-left: 36px;
  box-sizing: border-box;
}

/* Connecting Timeline Axis */
.schedule-timeline::before {
  content: '';
  position: absolute;
  top: 10px;
  bottom: 10px;
  left: 15px;
  width: 2px;
  background: var(--border);
}

.timeline-card {
  position: relative;
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-left: 4px solid var(--primary);
  border-radius: var(--radius-lg);
  padding: 20px;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  gap: 14px;
  transition: all var(--transition-smooth);
}

.timeline-card:hover {
  transform: translateX(6px);
  box-shadow: var(--shadow);
}

/* Indicator nodes */
.timeline-card::after {
  content: '';
  position: absolute;
  left: -27px;
  top: 24px;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background-color: var(--bg);
  border: 2px solid var(--primary);
  box-shadow: 0 0 0 4px var(--bg);
  transition: all var(--transition-smooth);
}

.timeline-card:hover::after {
  background-color: var(--primary);
  transform: scale(1.3);
  box-shadow: 0 0 8px var(--primary);
}

.timeline-card.urgent { border-left-color: var(--danger); }
.timeline-card.urgent::after { border-color: var(--danger); }
.timeline-card.urgent:hover::after { background-color: var(--danger); box-shadow: 0 0 8px var(--danger); }

.timeline-card.near-exam { border-left-color: var(--accent); }
.timeline-card.near-exam::after { border-color: var(--accent); }
.timeline-card.near-exam:hover::after { background-color: var(--accent); box-shadow: 0 0 8px var(--accent); }

.timeline-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid var(--border);
  padding-bottom: 8px;
}

.timeline-day {
  font-size: 14px;
  font-weight: 700;
  color: var(--primary);
}

.timeline-card.urgent .timeline-day { color: var(--danger); }
.timeline-card.near-exam .timeline-day { color: var(--accent); }

.timeline-meta-header {
  display: flex;
  align-items: center;
  gap: 12px;
}

.timeline-duration {
  font-size: 11px;
  font-weight: 700;
  background-color: var(--primary-glow);
  color: var(--primary);
  padding: 2px 8px;
  border-radius: 20px;
  letter-spacing: 0.3px;
}

.timeline-card.urgent .timeline-duration {
  background-color: rgba(229, 83, 75, 0.15);
  color: var(--danger);
}

.timeline-date {
  font-size: 11px;
  font-weight: 600;
  color: var(--text-dim);
}

/* Daily Focus style row */
.timeline-focus-box {
  background-color: var(--surface-2);
  border: 1px dashed var(--border);
  border-radius: var(--radius);
  padding: 10px 14px;
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
}

.focus-label {
  font-weight: 700;
  color: var(--text-dim);
}

.focus-text {
  font-weight: 600;
  color: var(--text);
}

/* Timeline Task Checklists */
.timeline-task-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.timeline-task-item {
  display: flex;
  align-items: flex-start;
}

.task-checkbox-label {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  cursor: pointer;
  width: 100%;
  font-size: 13px;
  color: var(--text);
  user-select: none;
}

.task-checkbox {
  display: none;
}

.task-checkbox-custom {
  width: 16px;
  height: 16px;
  border: 1.5px solid var(--border-light);
  border-radius: 4px;
  background-color: var(--surface-2);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-top: 2px;
  flex-shrink: 0;
  transition: all var(--transition-fast);
}

.task-checkbox-custom::after {
  content: '✓';
  color: #ffffff;
  font-size: 11px;
  font-weight: bold;
  opacity: 0;
  transition: opacity var(--transition-fast);
}

.task-checkbox:checked + .task-checkbox-custom {
  background-color: var(--success);
  border-color: var(--success);
  box-shadow: 0 0 5px rgba(63, 185, 80, 0.3);
}

.task-checkbox:checked + .task-checkbox-custom::after {
  opacity: 1;
}

.task-text {
  line-height: 1.4;
  transition: all var(--transition-smooth);
}

.task-checkbox:checked ~ .task-text {
  color: var(--text-muted);
  text-decoration: line-through;
}

/* Study Prep Tips block */
.timeline-tip-box {
  background-color: rgba(var(--surface-3-rgb), 0.35);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius-sm);
  padding: 10px 14px;
  display: flex;
  align-items: flex-start;
  gap: 8px;
  margin-top: 2px;
}

.tip-icon {
  font-size: 14px;
  flex-shrink: 0;
}

.tip-text {
  font-size: 12px;
  line-height: 1.5;
  color: var(--text-dim);
  margin: 0;
}

.tip-text strong {
  font-weight: 700;
  color: var(--text);
}

/* Animations */
@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

@keyframes float {
  0% { transform: translateY(0px); }
  50% { transform: translateY(-8px); }
  100% { transform: translateY(0px); }
}

@keyframes slideDown {
  from { transform: translateY(-100%); }
  to { transform: translateY(0); }
}

@keyframes cardAppear {
  from {
    opacity: 0;
    transform: translateY(15px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Mobile Responsiveness */
/* --- Tablet & Mobile Responsiveness --- */

/* Medium & Small Tablets / Large Mobiles (e.g. iPad, foldables, small width laptops) */
@media (max-width: 1024px) {
  .options-panel {
    width: 280px;
    padding: 20px;
  }
}

/* Mobiles & Small Tablets (e.g. portrait tablets, all smartphones) */
@media (max-width: 820px) {
  /* Header Wrapping System */
  .hub-header {
    height: auto !important;
    min-height: 100px;
    flex-wrap: wrap !important;
    padding: 12px 16px !important;
    gap: 12px !important;
    justify-content: space-between !important;
  }
  
  .hub-header .header-left {
    flex: 1 1 auto !important;
  }
  
  .hub-header .header-right {
    flex: 0 0 auto !important;
    display: flex !important;
    align-items: center !important;
    gap: 8px !important;
  }
  
  .hub-header .header-center {
    flex: 1 1 100% !important; /* Force to take full width and wrap to row 2 */
    order: 3 !important;       /* Push below left and right sections */
    display: flex !important;
    justify-content: center !important;
  }
  
  .hub-header .tabs-navigation {
    width: 100% !important;
    justify-content: center !important;
  }
  
  .hub-header .tab-btn {
    flex: 1 !important;
    text-align: center !important;
    padding: 8px 10px !important;
    font-size: 12px !important;
  }

  /* Split Layout Columns Stack */
  .hub-main-content {
    overflow-y: auto !important; /* Allow the entire main area to scroll as one single page */
  }
  
  .hub-view.active {
    height: auto !important;
  }

  .split-layout {
    flex-direction: column !important;
    height: auto !important;
    overflow: visible !important;
  }
  
  .options-panel {
    width: 100% !important;
    height: auto !important;
    overflow: visible !important;
    border-right: none !important;
    border-bottom: 1px solid var(--border) !important;
    padding: 24px 20px !important;
    box-sizing: border-box !important;
    flex-shrink: 0 !important;
  }
  
  .output-workspace {
    width: 100% !important;
    height: auto !important;
    overflow: visible !important;
    padding: 24px 20px !important;
    box-sizing: border-box !important;
  }
  
  /* Timeline Adjustments */
  .schedule-timeline {
    padding-left: 24px !important;
  }
  
  .schedule-timeline::before {
    left: 8px !important;
  }
  
  .timeline-card::after {
    left: -21px !important;
  }
}

/* Small Smart Phones (e.g. iPhone SE, mini/compact screens, android brands) */
@media (max-width: 480px) {
  .hub-header {
    padding: 10px 12px !important;
    gap: 8px !important;
  }
  
  .hub-header .brand-h1 {
    font-size: 14px !important;
  }
  
  .hub-header .header-left {
    gap: 8px !important;
  }

  .options-panel,
  .output-workspace {
    padding: 20px 16px !important;
  }
  
  /* Dropdowns */
  .history-dropdown {
    width: calc(100vw - 32px) !important;
    max-width: 320px !important;
  }
  
  .shapes-dropdown-panel {
    width: calc(100vw - 32px) !important;
    max-width: 340px !important;
  }

  .shapes-dropdown-panel .shapes-grid {
    grid-template-columns: repeat(auto-fill, minmax(34px, 1fr)) !important;
  }
  
  /* Timeline Elements */
  .timeline-header {
    flex-direction: column !important;
    align-items: flex-start !important;
    gap: 8px !important;
  }
  
  .timeline-meta-header {
    width: 100% !important;
    justify-content: space-between !important;
  }
  
  /* LeetCode Challenges Column Layout on Small Screens */
  .timeline-leetcode-box li.timeline-task-item {
    flex-direction: column !important;
    align-items: flex-start !important;
    gap: 8px !important;
  }
  
  .timeline-leetcode-box a.leetcode-link {
    margin-left: 26px !important;
    align-self: flex-start !important;
  }

  /* Flashcards Grid scaling */
  .flashcards-grid {
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)) !important;
    gap: 16px !important;
  }

  .flashcard.has-recall {
    height: 380px; /* Taller card to fit layout shifts gracefully */
  }
}

/* --- Flowchart Maker Canvas & New Top Toolbar --- */
.canvas-toolbar {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 6px 12px;
  margin-bottom: 12px;
  z-index: 1000;
  box-shadow: var(--shadow-sm);
  position: relative;
  user-select: none;
  flex-wrap: wrap;
}

.canvas-toolbar .toolbar-btn {
  appearance: none !important;
  -webkit-appearance: none !important;
  background: var(--surface) !important;
  border: 1px solid var(--border) !important;
  color: var(--text) !important;
  border-radius: var(--radius) !important;
  padding: 6px 14px !important;
  height: 34px !important;
  width: auto !important;
  font-size: 13px !important;
  font-weight: 600 !important;
  font-family: var(--font-sans, system-ui, -apple-system, sans-serif) !important;
  cursor: pointer !important;
  display: inline-flex !important;
  align-items: center !important;
  gap: 7px !important;
  white-space: nowrap !important;
  flex-shrink: 0 !important;
  transition: background 0.15s ease, border-color 0.15s ease, box-shadow 0.15s ease !important;
  box-shadow: 0 1px 3px rgba(0,0,0,0.06) !important;
}

.canvas-toolbar .toolbar-btn:hover {
  background: var(--surface-hover) !important;
  border-color: var(--primary) !important;
  box-shadow: 0 2px 6px rgba(0,0,0,0.1) !important;
}

.canvas-toolbar .toolbar-btn:active {
  transform: scale(0.97) !important;
}

.canvas-toolbar .toolbar-btn.danger {
  color: var(--danger) !important;
  border-color: rgba(229, 83, 75, 0.3) !important;
}

.canvas-toolbar .toolbar-btn.danger:hover {
  background: rgba(229, 83, 75, 0.1) !important;
  border-color: var(--danger) !important;
}

.canvas-toolbar .toolbar-icon {
  width: 16px;
  height: 16px;
  flex-shrink: 0;
}

.canvas-toolbar .chevron-icon {
  width: 12px;
  height: 12px;
  opacity: 0.5;
  margin-left: 2px;
  flex-shrink: 0;
}

/* Floating Shapes Dropdown Grid Panel */
.dropdown-trigger-wrapper {
  position: relative;
}

.shapes-dropdown-panel {
  position: absolute;
  top: calc(100% + 8px);
  left: 0;
  width: 340px;
  max-height: 70vh;
  overflow-y: auto;
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  padding: 12px;
  z-index: 10000;
  display: flex;
  flex-direction: column;
  gap: 10px;
  animation: dropdownFadeIn 0.2s cubic-bezier(0.16, 1, 0.3, 1) both;
}

/* Custom scrollbar for the shapes panel */
.shapes-dropdown-panel::-webkit-scrollbar {
  width: 6px;
}
.shapes-dropdown-panel::-webkit-scrollbar-track {
  background: transparent;
}
.shapes-dropdown-panel::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 3px;
}
.shapes-dropdown-panel::-webkit-scrollbar-thumb:hover {
  background: var(--text-muted);
}

.shapes-dropdown-panel.hidden {
  display: none;
}

.shapes-dropdown-section {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border);
}

.shapes-dropdown-section:last-child {
  border-bottom: none;
  padding-bottom: 0;
}

.shapes-section-title {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--primary);
  letter-spacing: 0.6px;
  padding: 2px 0;
}

.shapes-grid {
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  gap: 4px;
}

.shapes-dropdown-panel .shape-btn {
  background: var(--surface-2) !important;
  border: 1px solid transparent !important;
  border-radius: var(--radius-sm) !important;
  color: var(--text) !important;
  padding: 4px !important;
  cursor: pointer !important;
  display: flex !important;
  flex-direction: row !important;
  align-items: center !important;
  justify-content: center !important;
  gap: 0 !important;
  transition: all var(--transition-fast) !important;
  width: 34px !important;
  height: 34px !important;
  box-sizing: border-box !important;
}

.shapes-dropdown-panel .shape-btn:hover {
  background-color: var(--primary-glow) !important;
  border-color: var(--primary) !important;
  color: var(--primary) !important;
  transform: scale(1.1) !important;
}

.shapes-dropdown-panel .shape-btn svg {
  width: 20px !important;
  height: 20px !important;
  fill: none !important;
  stroke: currentColor !important;
  stroke-width: 1.5px !important;
  flex-shrink: 0 !important;
}

/* Canvas Area Container */
.flowchart-canvas-container {
  width: 100%;
  height: 100%;
  min-height: 550px;
  overflow: auto;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background-color: var(--surface);
  position: relative;
  box-shadow: var(--shadow-sm);
}

.flowchart-canvas {
  width: 1500px;
  height: 1200px;
  background-image: radial-gradient(var(--border) 1px, transparent 1px);
  background-size: 20px 20px;
  position: relative;
  overflow: hidden;
}

/* Unified Shape Nodes on Canvas */
.flowchart-shape {
  position: absolute;
  min-width: 40px;
  min-height: 20px;
  cursor: move;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 10px;
  box-sizing: border-box;
  user-select: none;
}

.flowchart-shape svg {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: -1;
  overflow: visible;
}

.flowchart-shape svg rect,
.flowchart-shape svg polygon,
.flowchart-shape svg circle,
.flowchart-shape svg ellipse,
.flowchart-shape svg path {
  fill: var(--surface-2);
  stroke: var(--border);
  stroke-width: 2;
  transition: fill var(--transition-smooth), stroke var(--transition-smooth);
}

.flowchart-shape:hover svg rect,
.flowchart-shape:hover svg polygon,
.flowchart-shape:hover svg circle,
.flowchart-shape:hover svg ellipse,
.flowchart-shape:hover svg path {
  stroke: var(--text-dim);
}

/* Custom Outlines for Selected Elements */
.flowchart-shape.selected {
  z-index: 100;
  outline: 1.5px dashed var(--primary);
  outline-offset: 4px;
}

.flowchart-shape.selected svg rect,
.flowchart-shape.selected svg polygon,
.flowchart-shape.selected svg circle,
.flowchart-shape.selected svg ellipse,
.flowchart-shape.selected svg path {
  stroke: var(--primary);
  fill: var(--primary-glow);
}

/* Specialized Shapes: Textbox */
.shape-textbox {
  background-color: transparent !important;
}

.shape-textbox svg {
  display: none;
}

.shape-textbox.selected {
  outline: 1.5px dashed var(--primary);
}

/* Specialized Shapes: Picture */
.shape-picture {
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
  border-radius: var(--radius-sm);
}

.shape-picture svg {
  display: none;
}

/* Specialized Shapes: Lines and Arrows */
.shape-line,
.shape-line-up,
.shape-line-h,
.shape-line-v,
.shape-curve,
.shape-arrow,
.shape-arrow-up,
.shape-double-arrow,
.shape-elbow,
.shape-elbow-up {
  padding: 0;
  cursor: pointer;
}

.shape-line svg,
.shape-line-up svg,
.shape-line-h svg,
.shape-line-v svg,
.shape-curve svg,
.shape-arrow svg,
.shape-arrow-up svg,
.shape-double-arrow svg,
.shape-elbow svg,
.shape-elbow-up svg {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 1;
}

.shape-line svg line,
.shape-line-up svg line,
.shape-line-h svg line,
.shape-line-v svg line,
.shape-curve svg path,
.shape-arrow svg line,
.shape-arrow-up svg line,
.shape-double-arrow svg line,
.shape-elbow svg path,
.shape-elbow-up svg path {
  fill: none !important;
  stroke: var(--primary) !important;
  stroke-width: 2.5px !important;
  transition: stroke var(--transition-fast);
}

.shape-line:hover svg line,
.shape-line-up:hover svg line,
.shape-line-h:hover svg line,
.shape-line-v:hover svg line,
.shape-curve:hover svg path,
.shape-arrow:hover svg line,
.shape-arrow-up:hover svg line,
.shape-double-arrow:hover svg line,
.shape-elbow:hover svg path,
.shape-elbow-up:hover svg path {
  stroke: var(--primary-strong) !important;
}

.shape-line.selected svg line,
.shape-line-up.selected svg line,
.shape-line-h.selected svg line,
.shape-line-v.selected svg line,
.shape-curve.selected svg path,
.shape-arrow.selected svg line,
.shape-arrow.selected svg line,
.shape-arrow-up.selected svg line,
.shape-double-arrow.selected svg line,
.shape-elbow.selected svg path,
.shape-elbow-up.selected svg path {
  stroke: var(--primary-strong) !important;
}

/* Resize Handles */
.resize-handle {
  position: absolute;
  width: 8px;
  height: 8px;
  background-color: var(--primary);
  border: 1px solid #ffffff;
  border-radius: 1px;
  z-index: 1000;
  display: none;
}

.flowchart-shape.selected .resize-handle {
  display: block;
}

.resize-handle.tl { top: -4px; left: -4px; cursor: nwse-resize; }
.resize-handle.tr { top: -4px; right: -4px; cursor: nesw-resize; }
.resize-handle.bl { bottom: -4px; left: -4px; cursor: nesw-resize; }
.resize-handle.br { bottom: -4px; right: -4px; cursor: nwse-resize; }

/* Text Content Input */
.shape-text-container {
  width: 100%;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  z-index: 5;
  pointer-events: none;
}

.shape-label-span {
  font-size: 12px;
  font-weight: 500;
  color: var(--text);
  text-align: center;
  word-break: break-word;
  max-width: 100%;
  max-height: 100%;
  line-height: 1.3;
}

.shape-text-input {
  width: 90%;
  background: transparent;
  border: none;
  outline: none;
  font-size: 12px;
  font-weight: 500;
  color: var(--text);
  text-align: center;
  font-family: var(--font-sans);
  pointer-events: auto;
  padding: 2px;
}

/* Textbox Container */
.textbox-container {
  border: 1.5px dashed var(--border);
  border-radius: var(--radius-sm);
  padding: 8px;
  min-height: 20px;
}

.flowchart-shape.selected .textbox-container {
  border-color: var(--primary);
}

/* Picture Shape */
.shape-picture-img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  border-radius: var(--radius-sm);
  pointer-events: none;
  border: 1px solid var(--border);
}

.flowchart-shape.selected .shape-picture-img {
  border-color: var(--primary);
}

/* Line shapes - allow pointer events on the SVG */
.flowchart-shape.line-shape {
  padding: 0;
  pointer-events: none;
}

.flowchart-shape.line-shape svg {
  pointer-events: all;
}

.flowchart-shape.line-shape .resize-handle {
  pointer-events: auto;
}

/* Code Blocks in Flashcards */
.code-block-flashcard {
  background-color: #1a1a24;
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 6px;
  padding: 8px 12px;
  margin: 8px 0;
  overflow-x: auto;
  text-align: left;
  max-width: 100%;
  flex-shrink: 0;
  width: 100%;
  box-sizing: border-box;
}

.code-block-flashcard code {
  font-family: 'JetBrains Mono', 'Fira Code', monospace;
  font-size: 11px;
  color: #38bdf8; /* light blue for code */
  white-space: pre;
}

/* Inline Code in Flashcards */
.inline-code-flashcard {
  font-family: 'JetBrains Mono', 'Fira Code', monospace;
  background-color: rgba(255, 255, 255, 0.15);
  border-radius: 4px;
  padding: 1px 4px;
  font-size: 11px;
  color: #fb7185; /* light rose color */
  font-weight: 500;
}

/* General Flashcard Question Text Styling */
.flashcard-question-text {
  font-size: 14px;
  font-weight: 600;
  line-height: 1.5;
  text-align: center;
  max-width: 90%;
  flex-shrink: 0;
}

/* Custom tall layout for flashcards with code recall input */
.flashcard.has-recall {
  height: 340px; /* Taller card to fit code block and input */
}

.flashcard.has-recall .flashcard-front {
  justify-content: flex-start;
  padding-top: 35px; /* Leave space for index and category badges */
  gap: 8px;
}

.flashcard.has-recall .flashcard-question-text {
  width: 100%;
  font-size: 13px;
  line-height: 1.4;
  margin-top: 8px;
  text-align: center;
}

.flashcard.has-recall .card-recall-container {
  width: 100%;
  flex-shrink: 0;
  margin-top: auto; /* Push input section to the bottom of card */
}