/* ============================================================
   数字图像处理智慧教学平台 — Custom Styles
   Extends Tailwind CSS with animations, components, and layout
   ============================================================ */

/* ----- CSS Custom Properties ----- */
:root {
  /* Primary (Indigo) */
  --color-primary-50:  #eef2ff;
  --color-primary-100: #e0e7ff;
  --color-primary-200: #c7d2fe;
  --color-primary-300: #a5b4fc;
  --color-primary-400: #818cf8;
  --color-primary-500: #6366f1;
  --color-primary-600: #4f46e5;
  --color-primary-700: #4338ca;
  --color-primary-800: #3730a3;
  --color-primary-900: #312e81;

  /* Accent (Teal) */
  --color-accent-50:  #f0fdfa;
  --color-accent-100: #ccfbf1;
  --color-accent-200: #99f6e4;
  --color-accent-300: #5eead4;
  --color-accent-400: #2dd4bf;
  --color-accent-500: #14b8a6;
  --color-accent-600: #0d9488;
  --color-accent-700: #0f766e;
  --color-accent-800: #115e59;
  --color-accent-900: #134e4a;

  /* Neutrals */
  --color-bg:         #f9fafb;
  --color-surface:    #ffffff;
  --color-border:     #e5e7eb;
  --color-text:       #1f2937;
  --color-text-light: #6b7280;

  /* Shadows */
  --shadow-sm:  0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md:  0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
  --shadow-lg:  0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -4px rgba(0, 0, 0, 0.04);
  --shadow-xl:  0 20px 25px -5px rgba(0, 0, 0, 0.08), 0 8px 10px -6px rgba(0, 0, 0, 0.04);

  /* Radii */
  --radius-sm: 6px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;

  /* Transitions */
  --transition-fast:   150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-normal: 250ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow:   350ms cubic-bezier(0.4, 0, 0.2, 1);
}


/* ============================================================
   KEYFRAME ANIMATIONS
   ============================================================ */

/* Fade In — used for page / route transitions */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* Slide In — sidebar items entering from the left */
@keyframes slideIn {
  from { opacity: 0; transform: translateX(-16px); }
  to   { opacity: 1; transform: translateX(0); }
}

/* Scale In — modal / dialog pop */
@keyframes scaleIn {
  from { opacity: 0; transform: scale(0.92); }
  to   { opacity: 1; transform: scale(1); }
}

/* Pulse — loading / skeleton states */
@keyframes pulse {
  0%, 100% { opacity: 1; }
  50%      { opacity: 0.4; }
}

/* Spin — for loading spinners */
@keyframes spin {
  to { transform: rotate(360deg); }
}

/* Gradient shift — login background */
@keyframes gradientShift {
  0%   { background-position: 0% 50%; }
  50%  { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

/* Float — subtle floating motion for decorative elements */
@keyframes float {
  0%, 100% { transform: translateY(0); }
  50%      { transform: translateY(-10px); }
}

/* Utility classes for animations */
.animate-fade-in    { animation: fadeIn var(--transition-slow) ease-out both; }
.animate-slide-in   { animation: slideIn var(--transition-slow) ease-out both; }
.animate-scale-in   { animation: scaleIn var(--transition-normal) ease-out both; }
.animate-pulse-soft { animation: pulse 2s cubic-bezier(0.4, 0, 0.6, 1) infinite; }
.animate-spin       { animation: spin 0.8s linear infinite; }
.animate-float      { animation: float 4s ease-in-out infinite; }

/* Stagger children */
.stagger-children > *:nth-child(1) { animation-delay: 0ms; }
.stagger-children > *:nth-child(2) { animation-delay: 60ms; }
.stagger-children > *:nth-child(3) { animation-delay: 120ms; }
.stagger-children > *:nth-child(4) { animation-delay: 180ms; }
.stagger-children > *:nth-child(5) { animation-delay: 240ms; }
.stagger-children > *:nth-child(6) { animation-delay: 300ms; }
.stagger-children > *:nth-child(7) { animation-delay: 360ms; }
.stagger-children > *:nth-child(8) { animation-delay: 420ms; }


/* ============================================================
   SCROLLBAR
   ============================================================ */
::-webkit-scrollbar {
  width: 6px;
  height: 6px;
}

::-webkit-scrollbar-track {
  background: transparent;
}

::-webkit-scrollbar-thumb {
  background: var(--color-primary-200);
  border-radius: 999px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--color-primary-400);
}

/* Firefox */
* {
  scrollbar-width: thin;
  scrollbar-color: var(--color-primary-200) transparent;
}


/* ============================================================
   BASE / GLOBAL
   ============================================================ */
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
               "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue",
               Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Vue route transition wrapper */
.page-enter-active {
  animation: fadeIn var(--transition-slow) ease-out;
}


/* ============================================================
   COMPONENT: Card
   ============================================================ */
.card {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--color-border);
  padding: 1.5rem;
  transition: box-shadow var(--transition-normal),
              transform var(--transition-normal);
}

.card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}

.card-flat {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
  padding: 1.5rem;
}

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

.card-header h3 {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--color-text);
}


/* ============================================================
   COMPONENT: Buttons
   ============================================================ */

/* Primary — gradient indigo */
.btn-primary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.6rem 1.5rem;
  font-size: 0.875rem;
  font-weight: 600;
  color: #fff;
  background: linear-gradient(135deg, var(--color-primary-500), var(--color-primary-700));
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-normal);
  box-shadow: 0 2px 8px rgba(99, 102, 241, 0.35);
  position: relative;
  overflow: hidden;
}

.btn-primary::after {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(255,255,255,0.15), transparent);
  opacity: 0;
  transition: opacity var(--transition-fast);
}

.btn-primary:hover {
  transform: translateY(-1px);
  box-shadow: 0 4px 14px rgba(99, 102, 241, 0.45);
}

.btn-primary:hover::after {
  opacity: 1;
}

.btn-primary:active {
  transform: translateY(0);
  box-shadow: 0 1px 4px rgba(99, 102, 241, 0.3);
}

.btn-primary:disabled {
  opacity: 0.55;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

/* Secondary — outlined */
.btn-secondary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.6rem 1.5rem;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-primary-600);
  background: transparent;
  border: 1.5px solid var(--color-primary-300);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-normal);
}

.btn-secondary:hover {
  background: var(--color-primary-50);
  border-color: var(--color-primary-500);
  color: var(--color-primary-700);
}

.btn-secondary:active {
  background: var(--color-primary-100);
}

/* Danger */
.btn-danger {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.6rem 1.5rem;
  font-size: 0.875rem;
  font-weight: 600;
  color: #fff;
  background: linear-gradient(135deg, #ef4444, #dc2626);
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-normal);
  box-shadow: 0 2px 8px rgba(239, 68, 68, 0.3);
}

.btn-danger:hover {
  transform: translateY(-1px);
  box-shadow: 0 4px 14px rgba(239, 68, 68, 0.4);
}

.btn-danger:active {
  transform: translateY(0);
}

/* Small variant */
.btn-sm {
  padding: 0.35rem 0.9rem;
  font-size: 0.8rem;
}

/* Icon-only button */
.btn-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.25rem;
  height: 2.25rem;
  padding: 0;
  border-radius: var(--radius-md);
  color: var(--color-text-light);
  background: transparent;
  border: 1px solid transparent;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.btn-icon:hover {
  background: var(--color-primary-50);
  color: var(--color-primary-600);
  border-color: var(--color-primary-200);
}


/* ============================================================
   COMPONENT: Input Field
   ============================================================ */
.input-field {
  width: 100%;
  padding: 0.6rem 0.9rem;
  font-size: 0.875rem;
  color: var(--color-text);
  background: var(--color-surface);
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-md);
  outline: none;
  transition: border-color var(--transition-fast),
              box-shadow var(--transition-fast);
}

.input-field::placeholder {
  color: #9ca3af;
}

.input-field:focus {
  border-color: var(--color-primary-400);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.12);
}

.input-field:disabled {
  background: #f3f4f6;
  cursor: not-allowed;
  opacity: 0.7;
}

/* Label */
.input-label {
  display: block;
  margin-bottom: 0.35rem;
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--color-text-light);
}

/* Textarea variant */
textarea.input-field {
  resize: vertical;
  min-height: 5rem;
  line-height: 1.6;
}

/* Select variant */
select.input-field {
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%236b7280' d='M6 8.825a.5.5 0 0 1-.354-.146l-4-4a.5.5 0 0 1 .708-.708L6 7.617l3.646-3.646a.5.5 0 0 1 .708.708l-4 4A.5.5 0 0 1 6 8.825z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.75rem center;
  padding-right: 2.25rem;
}


/* ============================================================
   COMPONENT: Sidebar Item
   ============================================================ */
.sidebar-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.65rem 1rem;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-text-light);
  border-radius: var(--radius-md);
  border-left: 3px solid transparent;
  cursor: pointer;
  transition: all var(--transition-fast);
  text-decoration: none;
  animation: slideIn var(--transition-slow) ease-out both;
}

.sidebar-item:hover {
  background: var(--color-primary-50);
  color: var(--color-primary-700);
}

.sidebar-item.active {
  background: var(--color-primary-50);
  color: var(--color-primary-700);
  border-left-color: var(--color-primary-500);
  font-weight: 600;
}

.sidebar-item .icon {
  width: 1.25rem;
  height: 1.25rem;
  flex-shrink: 0;
  opacity: 0.75;
}

.sidebar-item.active .icon {
  opacity: 1;
}


/* ============================================================
   COMPONENT: Stat Card (Dashboard)
   ============================================================ */
.stat-card {
  display: flex;
  align-items: flex-start;
  gap: 1rem;
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
  padding: 1.25rem 1.5rem;
  transition: all var(--transition-normal);
}

.stat-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.stat-card .stat-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 3rem;
  height: 3rem;
  border-radius: var(--radius-md);
  flex-shrink: 0;
}

.stat-card .stat-icon.primary   { background: var(--color-primary-100); color: var(--color-primary-600); }
.stat-card .stat-icon.accent    { background: var(--color-accent-100);  color: var(--color-accent-600); }
.stat-card .stat-icon.warning   { background: #fef3c7; color: #d97706; }
.stat-card .stat-icon.danger    { background: #fee2e2; color: #dc2626; }
.stat-card .stat-icon.success   { background: #d1fae5; color: #059669; }

.stat-card .stat-info {
  flex: 1;
  min-width: 0;
}

.stat-card .stat-value {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-text);
  line-height: 1.2;
}

.stat-card .stat-label {
  font-size: 0.8rem;
  color: var(--color-text-light);
  margin-top: 0.15rem;
}

.stat-card .stat-change {
  font-size: 0.75rem;
  font-weight: 500;
  margin-top: 0.25rem;
}

.stat-card .stat-change.up   { color: #059669; }
.stat-card .stat-change.down { color: #dc2626; }


/* ============================================================
   COMPONENT: Knowledge Graph Node
   ============================================================ */
.knowledge-node {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
  padding: 1rem 1.25rem;
  background: var(--color-surface);
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition: all var(--transition-normal);
  text-align: center;
  min-width: 120px;
}

.knowledge-node:hover {
  border-color: var(--color-primary-400);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.08), var(--shadow-md);
  transform: translateY(-3px);
}

.knowledge-node.completed {
  border-color: var(--color-accent-400);
  background: var(--color-accent-50);
}

.knowledge-node.locked {
  opacity: 0.5;
  cursor: not-allowed;
}

.knowledge-node .node-icon {
  width: 2.5rem;
  height: 2.5rem;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  background: var(--color-primary-100);
  color: var(--color-primary-600);
  font-size: 1.1rem;
}

.knowledge-node.completed .node-icon {
  background: var(--color-accent-100);
  color: var(--color-accent-700);
}

.knowledge-node .node-label {
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--color-text);
}


/* ============================================================
   COMPONENT: Simulation Canvas
   ============================================================ */
.simulation-canvas {
  position: relative;
  background: #0f172a;
  border: 2px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  aspect-ratio: 16 / 10;
}

.simulation-canvas canvas,
.simulation-canvas img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: contain;
}

.simulation-canvas .canvas-overlay {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(15, 23, 42, 0.6);
  color: #fff;
  font-size: 0.9rem;
  opacity: 0;
  transition: opacity var(--transition-fast);
}

.simulation-canvas:hover .canvas-overlay {
  opacity: 1;
}

.simulation-canvas .canvas-toolbar {
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.5rem;
  background: linear-gradient(transparent, rgba(15, 23, 42, 0.85));
}


/* ============================================================
   COMPONENT: Badge
   ============================================================ */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 0.15rem 0.6rem;
  font-size: 0.7rem;
  font-weight: 600;
  border-radius: 999px;
  letter-spacing: 0.02em;
  white-space: nowrap;
}

.badge-primary { background: var(--color-primary-100); color: var(--color-primary-700); }
.badge-accent  { background: var(--color-accent-100);  color: var(--color-accent-700); }
.badge-success { background: #d1fae5; color: #065f46; }
.badge-warning { background: #fef3c7; color: #92400e; }
.badge-danger  { background: #fee2e2; color: #991b1b; }
.badge-info    { background: #dbeafe; color: #1e40af; }
.badge-neutral { background: #f3f4f6; color: #4b5563; }


/* ============================================================
   COMPONENT: Modal Overlay
   ============================================================ */
.modal-overlay {
  position: fixed;
  inset: 0;
  z-index: 1000;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(15, 23, 42, 0.5);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  animation: fadeIn 200ms ease-out;
}

.modal-overlay .modal-content {
  background: var(--color-surface);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-xl);
  width: 90%;
  max-width: 32rem;
  max-height: 85vh;
  overflow-y: auto;
  animation: scaleIn var(--transition-normal) ease-out;
}

.modal-overlay .modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.25rem 1.5rem;
  border-bottom: 1px solid var(--color-border);
}

.modal-overlay .modal-header h3 {
  font-size: 1.05rem;
  font-weight: 600;
}

.modal-overlay .modal-body {
  padding: 1.5rem;
}

.modal-overlay .modal-footer {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 0.75rem;
  padding: 1rem 1.5rem;
  border-top: 1px solid var(--color-border);
  background: #fafbfc;
  border-radius: 0 0 var(--radius-xl) var(--radius-xl);
}


/* ============================================================
   COMPONENT: Progress Ring
   ============================================================ */
.progress-ring {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.progress-ring svg {
  transform: rotate(-90deg);
}

.progress-ring .ring-bg {
  fill: none;
  stroke: var(--color-primary-100);
  stroke-width: 6;
}

.progress-ring .ring-fill {
  fill: none;
  stroke: var(--color-primary-500);
  stroke-width: 6;
  stroke-linecap: round;
  transition: stroke-dashoffset 0.6s ease;
}

.progress-ring .ring-label {
  position: absolute;
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--color-text);
}


/* ============================================================
   LOGIN PAGE
   ============================================================ */

/* Split-screen layout */
.login-page {
  display: flex;
  min-height: 100vh;
}

.login-page .login-left {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
  background: linear-gradient(-45deg,
    var(--color-primary-600),
    var(--color-primary-800),
    var(--color-accent-700),
    var(--color-primary-700));
  background-size: 400% 400%;
  animation: gradientShift 12s ease infinite;
  color: #fff;
  padding: 3rem;
}

.login-page .login-left::before,
.login-page .login-left::after {
  content: '';
  position: absolute;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.06);
}

.login-page .login-left::before {
  width: 400px;
  height: 400px;
  top: -80px;
  right: -100px;
  animation: float 6s ease-in-out infinite;
}

.login-page .login-left::after {
  width: 260px;
  height: 260px;
  bottom: -60px;
  left: -60px;
  animation: float 8s ease-in-out infinite reverse;
}

.login-page .login-left h1 {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 0.75rem;
  position: relative;
  z-index: 1;
}

.login-page .login-left p {
  font-size: 1rem;
  opacity: 0.85;
  max-width: 28rem;
  text-align: center;
  line-height: 1.7;
  position: relative;
  z-index: 1;
}

/* Right panel — form */
.login-page .login-right {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 3rem;
  background: var(--color-bg);
}

/* Glass-morphism card on the form side (optional layered effect) */
.login-card {
  width: 100%;
  max-width: 24rem;
  background: rgba(255, 255, 255, 0.75);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid rgba(255, 255, 255, 0.6);
  border-radius: var(--radius-xl);
  padding: 2.5rem;
  box-shadow: var(--shadow-xl);
}

.login-card h2 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 0.25rem;
}

.login-card .subtitle {
  font-size: 0.875rem;
  color: var(--color-text-light);
  margin-bottom: 2rem;
}

.login-card .form-group {
  margin-bottom: 1.25rem;
}

.login-card .login-btn {
  width: 100%;
  padding: 0.75rem;
  font-size: 0.95rem;
}


/* ============================================================
   TABLES (Admin / Teacher views)
   ============================================================ */
.data-table {
  width: 100%;
  border-collapse: separate;
  border-spacing: 0;
  font-size: 0.85rem;
}

.data-table thead th {
  position: sticky;
  top: 0;
  z-index: 10;
  background: #f8fafc;
  padding: 0.75rem 1rem;
  text-align: left;
  font-weight: 600;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--color-text-light);
  border-bottom: 2px solid var(--color-border);
  white-space: nowrap;
}

.data-table tbody td {
  padding: 0.75rem 1rem;
  color: var(--color-text);
  border-bottom: 1px solid #f1f5f9;
  vertical-align: middle;
}

.data-table tbody tr {
  transition: background var(--transition-fast);
}

.data-table tbody tr:hover {
  background: var(--color-primary-50);
}

.data-table tbody tr:last-child td {
  border-bottom: none;
}

/* Sortable header */
.data-table thead th.sortable {
  cursor: pointer;
  user-select: none;
}

.data-table thead th.sortable:hover {
  color: var(--color-primary-600);
}


/* ============================================================
   LAYOUT HELPERS
   ============================================================ */

/* Main content area with sidebar */
.app-layout {
  display: flex;
  min-height: 100vh;
}

.app-sidebar {
  width: 260px;
  flex-shrink: 0;
  background: var(--color-surface);
  border-right: 1px solid var(--color-border);
  padding: 1.5rem 1rem;
  display: flex;
  flex-direction: column;
  overflow-y: auto;
}

.app-main {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
}

.app-topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 3.75rem;
  padding: 0 1.5rem;
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  flex-shrink: 0;
}

.app-content {
  flex: 1;
  padding: 1.5rem;
  overflow-y: auto;
  animation: fadeIn var(--transition-slow) ease-out;
}


/* ============================================================
   RESPONSIVE
   ============================================================ */
/* Desktop: sidebar always visible, override any mobile transform */
@media (min-width: 1025px) {
  .mobile-sidebar {
    transform: none !important;
    transition: width 0.3s cubic-bezier(0.4, 0, 0.2, 1) !important;
    box-shadow: none !important;
  }
}

@media (max-width: 1024px) {
  .app-sidebar {
    width: 220px;
  }

  .stat-card .stat-value {
    font-size: 1.25rem;
  }

  /* Mobile sidebar: hidden by default, slides in when .open */
  .mobile-sidebar {
    transform: translateX(-100%);
    transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: none;
  }

  .mobile-sidebar.open {
    transform: translateX(0);
    box-shadow: 4px 0 24px rgba(0, 0, 0, 0.2);
  }
}

@media (max-width: 768px) {
  /* Login: stack vertically */
  .login-page {
    flex-direction: column;
  }

  .login-page .login-left {
    min-height: 200px;
    padding: 2rem;
  }

  .login-page .login-left h1 {
    font-size: 1.5rem;
  }

  .login-page .login-right {
    padding: 2rem 1.5rem;
  }

  .login-card {
    padding: 1.75rem;
  }

  /* Sidebar collapses to icons or hidden */
  .app-sidebar {
    position: fixed;
    left: 0;
    top: 0;
    bottom: 0;
    z-index: 50;
    width: 260px;
    transform: translateX(-100%);
    transition: transform var(--transition-normal);
    box-shadow: var(--shadow-xl);
  }

  .app-sidebar.open {
    transform: translateX(0);
  }

  .app-content {
    padding: 1rem;
  }

  /* Tables scroll horizontally */
  .data-table {
    display: block;
    overflow-x: auto;
    white-space: nowrap;
  }
}

@media (max-width: 480px) {
  .modal-overlay .modal-content {
    width: 95%;
    max-height: 90vh;
  }

  .card {
    padding: 1rem;
  }
}


/* ============================================================
   UTILITY CLASSES
   ============================================================ */

/* Truncate text */
.text-truncate {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

/* Glass effect */
.glass {
  background: rgba(255, 255, 255, 0.6);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid rgba(255, 255, 255, 0.4);
}

/* Gradient text */
.gradient-text {
  background: linear-gradient(135deg, var(--color-primary-500), var(--color-accent-500));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* Divider */
.divider {
  height: 1px;
  background: var(--color-border);
  margin: 1rem 0;
}

/* Skeleton loading placeholder */
.skeleton {
  background: linear-gradient(90deg, #f1f5f9 25%, #e2e8f0 50%, #f1f5f9 75%);
  background-size: 200% 100%;
  animation: pulse 1.8s ease-in-out infinite;
  border-radius: var(--radius-sm);
}

/* Focus-visible for accessibility */
*:focus-visible {
  outline: 2px solid var(--color-primary-400);
  outline-offset: 2px;
}

/* Smooth scrolling */
html {
  scroll-behavior: smooth;
}

/* Transition helper */
.transition-theme {
  transition: all var(--transition-normal);
}


/* ============================================================
   EXPERIMENT COVERS — Chapter-themed gradients
   ============================================================ */
.exp-cover-ch1  { background: linear-gradient(135deg, #2563eb, #4f46e5, #7c3aed); }
.exp-cover-ch2  { background: linear-gradient(135deg, #0891b2, #2563eb, #4338ca); }
.exp-cover-ch3  { background: linear-gradient(135deg, #059669, #0d9488, #0891b2); }
.exp-cover-ch4  { background: linear-gradient(135deg, #16a34a, #059669, #0d9488); }
.exp-cover-ch5  { background: linear-gradient(135deg, #f59e0b, #ea580c, #dc2626); }
.exp-cover-ch6  { background: linear-gradient(135deg, #f43f5e, #ec4899, #c026d3); }
.exp-cover-ch7  { background: linear-gradient(135deg, #7c3aed, #9333ea, #4f46e5); }
.exp-cover-ch8  { background: linear-gradient(135deg, #4f46e5, #2563eb, #0891b2); }
.exp-cover-ch9  { background: linear-gradient(135deg, #0d9488, #16a34a, #059669); }
.exp-cover-ch10 { background: linear-gradient(135deg, #ea580c, #f59e0b, #ca8a04); }
.exp-cover-ch11 { background: linear-gradient(135deg, #ec4899, #f43f5e, #dc2626); }
.exp-cover-ch12 { background: linear-gradient(135deg, #475569, #64748b, #52525b); }


/* ============================================================
   PHASE 4 — Interactive Demo Animations
   ============================================================ */

/* Convolution window sweep — slides a highlight across the image */
@keyframes sweep {
  0%   { transform: translateX(0); }
  100% { transform: translateX(calc(100% - 30px)); }
}

.animate-sweep {
  animation: sweep 2s ease-in-out infinite alternate;
}

/* Histogram bar morph — pulsing bar height for transition effect */
@keyframes morphBar {
  0%   { transform: scaleY(0.3); }
  50%  { transform: scaleY(1.0); }
  100% { transform: scaleY(0.3); }
}

.animate-morph-bar {
  animation: morphBar 1.5s ease-in-out infinite;
  transform-origin: bottom center;
}

/* Pixel highlight pulse — for convolution computation visualization */
@keyframes pixelHighlight {
  0%, 100% { box-shadow: 0 0 0 0 rgba(99, 102, 241, 0.4); }
  50%      { box-shadow: 0 0 0 6px rgba(99, 102, 241, 0); }
}

.animate-pixel-highlight {
  animation: pixelHighlight 1s ease-in-out infinite;
}

/* CDF curve draw animation */
@keyframes drawCurve {
  from { stroke-dashoffset: 1000; }
  to   { stroke-dashoffset: 0; }
}

.animate-draw-curve {
  stroke-dasharray: 1000;
  animation: drawCurve 2s ease-out forwards;
}

/* Kernel cell hover effect */
.kernel-cell {
  transition: all var(--transition-fast);
}

.kernel-cell:hover {
  transform: scale(1.1);
  z-index: 10;
}

/* Scan line animation for Fourier demo */
@keyframes scanLine {
  0%   { left: 0%; }
  100% { left: 100%; }
}

.animate-scan-line {
  animation: scanLine 3s linear infinite;
  position: absolute;
  top: 0;
  bottom: 0;
  width: 2px;
  background: rgba(239, 68, 68, 0.8);
  pointer-events: none;
}

/* Slide panel transition for result panels */
.slide-enter-active {
  animation: fadeIn var(--transition-slow) ease-out;
}

.slide-leave-active {
  animation: fadeIn var(--transition-normal) ease-in reverse;
}

/* ===== CodeEditor Component Styles ===== */
.code-editor-container .CodeMirror {
  height: auto;
  min-height: 300px;
  max-height: 500px;
  font-size: 13px;
  font-family: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', Consolas, monospace;
  border-radius: 0 0 0.75rem 0.75rem;
}
.code-editor-container .CodeMirror-scroll {
  min-height: 300px;
}
.code-editor-container .CodeMirror-gutters {
  background: #282a36;
  border-right: 1px solid #44475a;
}


/* ========================================
 *  Enhanced UI Styles (v2.1)
 * ======================================== */

/* Better card hover effects */
.card-lift {
  transition: transform 0.25s cubic-bezier(0.4, 0, 0.2, 1),
              box-shadow 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}
.card-lift:hover {
  transform: translateY(-3px);
  box-shadow: 0 12px 28px -8px rgba(0, 0, 0, 0.12),
              0 4px 12px -2px rgba(0, 0, 0, 0.06);
}

/* Gradient text utility */
.text-gradient-primary {
  background: linear-gradient(135deg, #4f46e5, #06b6d4);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* Enhanced button press feedback */
.btn-press:active {
  transform: scale(0.97);
  transition: transform 0.1s ease;
}

/* Glassmorphism card */
.glass-card {
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(12px);
  border: 1px solid rgba(255, 255, 255, 0.3);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.06);
}

/* Stat card with gradient icon background */
.stat-icon-gradient {
  background: linear-gradient(135deg, var(--color-primary-500), var(--color-primary-700));
  width: 48px;
  height: 48px;
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  flex-shrink: 0;
}

/* Smooth page transition */
.page-fade-enter {
  animation: fadeIn 0.3s ease-out forwards;
}

/* Experiment card thumbnail */
.exp-thumb-overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(to bottom, rgba(0,0,0,0) 0%, rgba(0,0,0,0.6) 100%);
  opacity: 0;
  transition: opacity 0.3s ease;
}
.exp-card:hover .exp-thumb-overlay {
  opacity: 1;
}

/* Skeleton shimmer for loading */
@keyframes shimmer {
  0% { background-position: -200% 0; }
  100% { background-position: 200% 0; }
}
.skeleton-shimmer {
  background: linear-gradient(90deg, #f1f5f9 25%, #e2e8f0 50%, #f1f5f9 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s ease-in-out infinite;
  border-radius: 8px;
}

/* Improved scrollbar */
.custom-scrollbar::-webkit-scrollbar {
  width: 6px;
}
.custom-scrollbar::-webkit-scrollbar-track {
  background: transparent;
}
.custom-scrollbar::-webkit-scrollbar-thumb {
  background: #cbd5e1;
  border-radius: 3px;
}
.custom-scrollbar::-webkit-scrollbar-thumb:hover {
  background: #94a3b8;
}

/* Tab indicator animation */
.tab-slide {
  position: relative;
}
.tab-slide::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 50%;
  width: 0;
  height: 2px;
  background: var(--color-primary-500);
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  transform: translateX(-50%);
}
.tab-slide:hover::after,
.tab-slide.active::after {
  width: 100%;
}

/* Dashboard welcome gradient */
.welcome-gradient {
  background: linear-gradient(135deg, #4f46e5 0%, #7c3aed 50%, #06b6d4 100%);
  background-size: 200% 200%;
  animation: gradientShift 8s ease infinite;
}

/* Badge pulse for notifications */
@keyframes badgePulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.1); }
}
.badge-pulse {
  animation: badgePulse 2s ease-in-out infinite;
}

/* Better focus ring */
.focus-ring:focus-visible {
  outline: 2px solid var(--color-primary-400);
  outline-offset: 2px;
  border-radius: 4px;
}


/* ============================================================
   WELCOME OVERLAY — Splash screen on portal entry
   ============================================================ */

/* Enter / leave transitions */
.welcome-fade-enter-active {
  animation: welcomeOverlayIn 0.5s cubic-bezier(0.16, 1, 0.3, 1) forwards;
}
.welcome-fade-leave-active {
  animation: welcomeOverlayOut 0.6s cubic-bezier(0.4, 0, 1, 1) forwards;
}

@keyframes welcomeOverlayIn {
  0%   { opacity: 0; }
  100% { opacity: 1; }
}
@keyframes welcomeOverlayOut {
  0%   { opacity: 1; }
  100% { opacity: 0; }
}

/* Logo entrance */
.welcome-logo {
  animation: welcomeLogoIn 0.7s cubic-bezier(0.16, 1, 0.3, 1) 0.15s both;
}
@keyframes welcomeLogoIn {
  0%   { opacity: 0; transform: scale(0.5) translateY(20px); }
  100% { opacity: 1; transform: scale(1) translateY(0); }
}

/* Title / subtitle entrance (staggered) */
.welcome-title {
  animation: welcomeTextIn 0.6s cubic-bezier(0.16, 1, 0.3, 1) 0.35s both;
}
.welcome-subtitle {
  animation: welcomeTextIn 0.6s cubic-bezier(0.16, 1, 0.3, 1) 0.5s both;
}
@keyframes welcomeTextIn {
  0%   { opacity: 0; transform: translateY(16px); }
  100% { opacity: 1; transform: translateY(0); }
}

/* Bouncing dots */
.welcome-dots {
  animation: welcomeTextIn 0.5s cubic-bezier(0.16, 1, 0.3, 1) 0.7s both;
}
.welcome-dot {
  animation: welcomeDotBounce 1.2s ease-in-out infinite;
}
@keyframes welcomeDotBounce {
  0%, 80%, 100% { transform: translateY(0); opacity: 0.4; }
  40%           { transform: translateY(-8px); opacity: 1; }
}

/* Decorative circles drift */
.welcome-circle-1 {
  animation: welcomeDrift1 8s ease-in-out infinite;
}
.welcome-circle-2 {
  animation: welcomeDrift2 10s ease-in-out infinite;
}
.welcome-circle-3 {
  animation: welcomeDrift3 7s ease-in-out infinite;
}
@keyframes welcomeDrift1 {
  0%, 100% { transform: translate(0, 0); }
  50%      { transform: translate(30px, 20px); }
}
@keyframes welcomeDrift2 {
  0%, 100% { transform: translate(0, 0); }
  50%      { transform: translate(-20px, -30px); }
}
@keyframes welcomeDrift3 {
  0%, 100% { transform: translate(0, 0); }
  50%      { transform: translate(15px, -15px); }
}