/* ========== CSS Variables (Apple Design) ========== */
:root {
  --primary: #007AFF;
  --primary-light: #409CFF;
  --primary-dark: #0056CC;
  --green: #34C759;
  --green-dark: #28A745;
  --red: #FF3B30;
  --orange: #FF9500;
  --yellow: #FFCC00;
  --bg: #F5F5F7;
  --card-bg: #FFFFFF;
  --text-primary: #1D1D1F;
  --text-secondary: #86868B;
  --text-light: #AEAEB2;
  --border: #E5E5EA;
  --separator: rgba(60, 60, 67, 0.12);
  --fill: rgba(120, 120, 128, 0.12);
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.04), 0 1px 2px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.06), 0 1px 4px rgba(0, 0, 0, 0.04);
  --shadow-lg: 0 20px 60px rgba(0, 0, 0, 0.12), 0 8px 20px rgba(0, 0, 0, 0.06);
  --radius: 16px;
  --radius-sm: 10px;
  --radius-lg: 20px;
  --transition: color 0.25s cubic-bezier(0.25,0.1,0.25,1), background-color 0.25s cubic-bezier(0.25,0.1,0.25,1), border-color 0.25s cubic-bezier(0.25,0.1,0.25,1), box-shadow 0.25s cubic-bezier(0.25,0.1,0.25,1), opacity 0.25s cubic-bezier(0.25,0.1,0.25,1), transform 0.25s cubic-bezier(0.25,0.1,0.25,1);
}

/* ========== Reset & Base ========== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: -apple-system, 'SF Pro Display', 'PingFang SC', 'Microsoft YaHei', 'Noto Sans CJK SC', sans-serif;
  background: var(--bg);
  color: var(--text-primary);
  font-size: 15px;
  line-height: 1.58;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a {
  color: var(--primary);
  text-decoration: none;
  transition: var(--transition);
}

a:hover {
  color: var(--primary-light);
}

/* ========== Typography (Apple Style) ========== */
h1 {
  font-size: 28px;
  font-weight: 700;
  letter-spacing: -0.025em;
  line-height: 1.15;
  color: var(--text-primary);
}

h2 {
  font-size: 22px;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.2;
  color: var(--text-primary);
}

h3 {
  font-size: 17px;
  font-weight: 600;
  line-height: 1.3;
  color: var(--text-primary);
}

h4 {
  font-size: 15px;
  font-weight: 600;
  line-height: 1.35;
  color: var(--text-primary);
}

.text-secondary {
  font-size: 13px;
  color: var(--text-secondary);
}

/* ========== Login Page (Apple Minimal) ========== */
.login-wrapper {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  background: var(--bg);
  position: relative;
  overflow: hidden;
}

/* Remove pseudo-element decorative circles (Apple doesn't decorate) */

.login-card {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  padding: 48px 40px;
  width: 420px;
  box-shadow: var(--shadow-lg);
  position: relative;
  z-index: 1;
  animation: fadeInUp 0.6s cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.login-card h1 {
  text-align: center;
  color: var(--text-primary);
  font-size: 28px;
  letter-spacing: -0.025em;
  margin-bottom: 8px;
  font-weight: 700;
}

.login-card .subtitle {
  text-align: center;
  color: var(--text-secondary);
  font-size: 14px;
  margin-bottom: 32px;
}

/* ========== Form Controls ========== */
.form-group {
  margin-bottom: 20px;
}

.form-group label {
  display: block;
  font-size: 14px;
  color: var(--text-primary);
  margin-bottom: 6px;
  font-weight: 500;
}

.form-group input,
.form-group select,
.form-group textarea {
  width: 100%;
  padding: 12px 16px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 15px;
  transition: var(--transition);
  outline: none;
  background: #FFFFFF;
  color: var(--text-primary);
  font-family: inherit;
}

.form-group input::placeholder,
.form-group select::placeholder,
.form-group textarea::placeholder {
  color: var(--text-light);
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(0, 122, 255, 0.15);
  background: #FFFFFF;
}

.form-group textarea {
  resize: vertical;
  min-height: 80px;
}

/* ========== Role Selector ========== */
.role-selector {
  display: flex;
  gap: 12px;
  margin-bottom: 24px;
}

.role-option {
  flex: 1;
  padding: 20px 16px;
  border: 2px solid var(--border);
  border-radius: var(--radius);
  text-align: center;
  cursor: pointer;
  transition: var(--transition);
  background: var(--card-bg);
}

.role-option:hover {
  border-color: var(--primary-light);
  background: var(--card-bg);
}

.role-option.active {
  border-color: var(--primary);
  background: rgba(0, 122, 255, 0.08);
}

.role-option .role-icon {
  font-size: 32px;
  margin-bottom: 8px;
  display: block;
  color: var(--text-secondary);
  transition: var(--transition);
}

.role-option .role-label {
  font-size: 15px;
  font-weight: 600;
  color: var(--text-primary);
  transition: var(--transition);
}

.role-option.active .role-label {
  color: var(--primary);
}

.role-option.active .role-icon {
  color: var(--primary);
}

/* ========== Buttons (Apple Style) ========== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 10px 24px;
  border: none;
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
  outline: none;
  font-family: inherit;
  -webkit-tap-highlight-color: transparent;

  &:disabled,
  &[disabled],
  &.is-disabled {
    opacity: 0.65;
    cursor: not-allowed;
  }

  &.is-loading {
    pointer-events: none;
    position: relative;

    &::after {
      content: '';
      width: 14px;
      height: 14px;
      border: 2px solid currentColor;
      border-right-color: transparent;
      border-radius: 50%;
      animation: spin 0.8s linear infinite;
      margin-left: 6px;
    }
  }
}

.btn:active {
  transform: scale(0.97);
  transition: transform 100ms ease-out;
}

.btn-primary {
  background: var(--primary);
  color: #FFFFFF;
  width: 100%;
  padding: 14px;
  font-size: 16px;
  font-weight: 600;
  border-radius: var(--radius-sm);
}

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

.btn-primary:active {
  transform: scale(0.97);
  transition: transform 100ms ease-out;
}

.btn-blue {
  background: var(--primary);
  color: #FFFFFF;
}

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

.btn-green {
  background: var(--green);
  color: #FFFFFF;
}

.btn-green:hover {
  background: var(--green-dark);
}

.btn-outline {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-primary);
}

.btn-outline:hover {
  border-color: var(--primary);
  color: var(--primary);
  background: rgba(0, 122, 255, 0.04);
}

.btn-sm {
  padding: 6px 14px;
  font-size: 13px;
}

.btn-danger {
  background: var(--red);
  color: #FFFFFF;
}

.btn-danger:hover {
  background: #E0332B;
}

.btn-pill {
  background: var(--primary);
  color: #FFFFFF;
  border-radius: 20px;
  padding: 8px 20px;
}

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

.login-switch {
  text-align: center;
  margin-top: 16px;
  font-size: 13px;
  color: var(--text-secondary);
}

.login-switch a {
  color: var(--primary);
  font-weight: 500;
}

/* ========== App Layout ========== */
.app-layout {
  display: flex;
  min-height: 100vh;
}

/* ========== Sidebar (Apple Frosted Glass) ========== */
.sidebar {
  width: 240px;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(40px) saturate(180%);
  -webkit-backdrop-filter: blur(40px) saturate(180%);
  color: var(--text-primary);
  display: flex;
  flex-direction: column;
  position: fixed;
  top: 0;
  left: 0;
  height: 100vh;
  z-index: 100;
  box-shadow: 0 0 0 0.5px var(--separator);
  overflow: hidden;
}

.sidebar-header {
  padding: 24px 20px;
  border-bottom: 0.5px solid var(--separator);
}

.sidebar-header h2 {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 4px;
  letter-spacing: -0.02em;
}

.sidebar-header .role-badge {
  font-size: 12px;
  background: var(--fill);
  color: var(--text-secondary);
  padding: 3px 10px;
  border-radius: 12px;
  display: inline-block;
}

.sidebar-nav {
  flex: 1;
  padding: 8px 0;
  overflow-y: auto;
  min-height: 0;
}

.nav-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 16px;
  margin: 2px 8px;
  color: var(--text-primary);
  cursor: pointer;
  transition: var(--transition);
  font-size: 14px;
  border-radius: 8px;
  border-left: none;
}

.nav-item:hover {
  background: var(--fill);
}

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

.nav-item .nav-icon {
  font-size: 18px;
  width: 24px;
  text-align: center;
}

.sidebar-footer {
  flex-shrink: 0;
  padding: 16px 20px;
  border-top: 0.5px solid var(--separator);
}

.sidebar-footer .user-info {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 12px;
}

.sidebar-footer .user-avatar {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: var(--fill);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 16px;
  color: var(--text-secondary);
  overflow: hidden;
}

.sidebar-footer .user-avatar-img {
  width: 100%;
  height: 100%;
  border-radius: 50%;
  object-fit: cover;
  display: block;
}

.sidebar-footer .user-name {
  font-size: 14px;
  font-weight: 500;
}

.sidebar-footer .btn-logout {
  display: block;
  width: 100%;
  padding: 8px;
  background: var(--fill);
  color: var(--text-primary);
  border: none;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 13px;
  font-family: inherit;
  transition: var(--transition);
}

.sidebar-footer .btn-logout:hover {
  background: rgba(120, 120, 128, 0.2);
}

.sidebar-footer .btn-logout:active {
  transform: scale(0.97);
  transition: transform 100ms ease-out;
}

/* ========== Main Content ========== */
.main-content {
  flex: 1;
  margin-left: 240px;
  padding: 24px;
  min-height: 100vh;
}

.page-header {
  margin-bottom: 24px;
}

.page-header h1 {
  font-size: 28px;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.025em;
}

.page-header p {
  color: var(--text-secondary);
  font-size: 14px;
  margin-top: 4px;
}

/* ========== KPI Cards ========== */
.kpi-row {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
  margin-bottom: 24px;
}

.kpi-card {
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
}

.kpi-card:hover {
  box-shadow: var(--shadow-md);
}

.kpi-card .kpi-label {
  font-size: 13px;
  color: var(--text-secondary);
  margin-bottom: 8px;
}

.kpi-card .kpi-value {
  font-size: 36px;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1;
  letter-spacing: -0.025em;
}

.kpi-card .kpi-icon {
  float: right;
  font-size: 32px;
  opacity: 0.15;
  color: var(--text-secondary);
}

/* ========== Cards & Panels ========== */
.card {
  background: var(--card-bg);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
  transition: var(--transition);
}

.card:hover {
  box-shadow: var(--shadow-md);
}

.card-header {
  padding: 16px 20px;
  border-bottom: 0.5px solid var(--separator);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.card-header h3 {
  font-size: 15px;
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 8px;
}

.card-body {
  padding: 20px;
}

.realtime-badge {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-size: 12px;
  color: var(--red);
  background: rgba(255, 59, 48, 0.08);
  padding: 3px 10px;
  border-radius: 12px;
}

.realtime-badge::before {
  content: '';
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--red);
  animation: pulse 1.5s infinite;
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.3; }
}

/* ========== Dashboard Grid ========== */
.dashboard-grid {
  display: grid;
  grid-template-columns: 300px 1fr 1fr;
  gap: 16px;
  align-items: start;
}

.dashboard-left { grid-column: 1; }
.dashboard-center { grid-column: 2; }
.dashboard-right { grid-column: 3; }

.chart-container {
  width: 100%;
  height: 320px;
}

/* ========== Sidebar Form (Teacher Left Panel) ========== */
.sidebar-form-section {
  margin-bottom: 20px;
}

.sidebar-form-section h4 {
  font-size: 14px;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 12px;
  display: flex;
  align-items: center;
  gap: 8px;
  padding-bottom: 8px;
  border-bottom: 0.5px solid var(--separator);
}

.counter-row {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 10px;
  font-size: 13px;
}

.counter-row .counter-label {
  width: 70px;
  color: var(--text-secondary);
  flex-shrink: 0;
}

.counter-row .counter-value {
  width: 50px;
  text-align: center;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 4px;
  font-size: 14px;
  font-weight: 600;
  background: #FFFFFF;
  transition: var(--transition);
}

.counter-row .counter-value:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(0, 122, 255, 0.15);
  outline: none;
}

.counter-row .btn-counter {
  width: 28px;
  height: 28px;
  border: 1px solid var(--border);
  background: #FFFFFF;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition);
  color: var(--text-primary);
}

.counter-row .btn-counter:hover {
  background: var(--primary);
  color: #FFFFFF;
  border-color: var(--primary);
}

.counter-row .btn-counter:active {
  transform: scale(0.97);
  transition: transform 100ms ease-out;
}

.score-input-row {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 10px;
  font-size: 13px;
}

.score-input-row .score-label {
  width: 50px;
  color: var(--text-secondary);
  flex-shrink: 0;
  font-size: 12px;
}

.score-input-row input {
  width: 70px;
  padding: 5px 8px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  text-align: center;
  font-size: 13px;
  font-family: inherit;
  background: #FFFFFF;
  color: var(--text-primary);
  transition: var(--transition);
}

.score-input-row input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(0, 122, 255, 0.15);
  outline: none;
}

.score-input-row .score-hint {
  font-size: 11px;
  color: var(--text-light);
}

/* ========== Student Detail Page ========== */
.student-detail-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}

.student-info-bar {
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 20px 24px;
  box-shadow: var(--shadow-sm);
  display: flex;
  align-items: center;
  gap: 20px;
  margin-bottom: 24px;
}

.student-avatar-lg {
  width: 64px;
  height: 64px;
  border-radius: 50%;
  background: var(--fill);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-secondary);
  font-size: 24px;
  font-weight: 700;
}

.student-meta h2 {
  font-size: 20px;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 4px;
}

.student-meta p {
  color: var(--text-secondary);
  font-size: 13px;
}

.student-meta .tag {
  display: inline-block;
  background: rgba(0, 122, 255, 0.08);
  color: var(--primary);
  padding: 2px 10px;
  border-radius: 10px;
  font-size: 12px;
  margin-right: 6px;
}

/* ========== Student Upload Page ========== */
.upload-zone {
  border: 2px dashed var(--border);
  border-radius: var(--radius-lg);
  padding: 60px 40px;
  text-align: center;
  cursor: pointer;
  transition: var(--transition);
  background: var(--card-bg);
  margin-bottom: 24px;
}

.upload-zone:hover,
.upload-zone.dragover {
  border-color: var(--primary);
  background: rgba(0, 122, 255, 0.03);
}

.upload-zone .upload-icon {
  font-size: 48px;
  margin-bottom: 16px;
  opacity: 0.4;
}

.upload-zone h3 {
  font-size: 17px;
  color: var(--text-primary);
  margin-bottom: 8px;
}

.upload-zone p {
  color: var(--text-secondary);
  font-size: 14px;
}

.upload-zone .file-types {
  margin-top: 12px;
  font-size: 12px;
  color: var(--text-light);
}

/* ========== Homework List ========== */
.homework-list {
  list-style: none;
}

.homework-item {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 16px 20px;
  border-bottom: 0.5px solid var(--separator);
  transition: var(--transition);
}

.homework-item:last-child {
  border-bottom: none;
}

.homework-item:hover {
  background: var(--fill);
}

.homework-item .hw-icon {
  font-size: 24px;
  width: 40px;
  text-align: center;
}

.homework-item .hw-info {
  flex: 1;
}

.homework-item .hw-name {
  font-size: 14px;
  font-weight: 500;
}

.homework-item .hw-date {
  font-size: 12px;
  color: var(--text-secondary);
  margin-top: 2px;
}

.hw-status {
  padding: 4px 12px;
  border-radius: 12px;
  font-size: 12px;
  font-weight: 500;
}

.hw-status.pending {
  background: rgba(255, 149, 0, 0.1);
  color: var(--orange);
}

.hw-status.graded {
  background: rgba(52, 199, 89, 0.1);
  color: var(--green);
}

.hw-status.reviewing {
  background: rgba(0, 122, 255, 0.1);
  color: var(--primary);
}

/* ========== Analysis Panel ========== */
.analysis-score {
  text-align: center;
  padding: 20px;
}

.analysis-score .big-score {
  font-size: 56px;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1;
  letter-spacing: -0.03em;
}

.analysis-score .score-label {
  font-size: 14px;
  color: var(--text-secondary);
  margin-top: 8px;
}

.score-breakdown {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

.breakdown-item {
  background: var(--bg);
  border-radius: var(--radius-sm);
  padding: 14px 16px;
}

.breakdown-item .bd-label {
  font-size: 12px;
  color: var(--text-secondary);
  margin-bottom: 4px;
}

.breakdown-item .bd-value {
  font-size: 22px;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.02em;
}

.breakdown-item .bd-bar {
  height: 4px;
  background: var(--border);
  border-radius: 2px;
  margin-top: 6px;
  overflow: hidden;
}

.breakdown-item .bd-bar-fill {
  height: 100%;
  border-radius: 2px;
  background: var(--primary);
  transition: width 0.6s cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

/* ========== AI Feedback (Apple Blue Tint) ========== */
.ai-feedback-card {
  background: rgba(0, 122, 255, 0.04);
  border: 1px solid rgba(0, 122, 255, 0.08);
  border-radius: var(--radius);
  padding: 20px;
  margin-top: 16px;
}

.ai-feedback-card h4 {
  font-size: 14px;
  color: var(--primary);
  margin-bottom: 10px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.ai-feedback-card .feedback-text {
  font-size: 13px;
  color: var(--text-primary);
  line-height: 1.8;
}

/* ========== Toast (Apple Frosted Glass) ========== */
.toast-container {
  position: fixed;
  top: 24px;
  right: 24px;
  z-index: 9999;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.toast {
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(20px) saturate(180%);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  border: 0.5px solid var(--separator);
  border-radius: 14px;
  padding: 14px 20px;
  box-shadow: var(--shadow-md);
  font-size: 14px;
  display: flex;
  align-items: center;
  gap: 10px;
  animation: slideIn 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94);
  min-width: 260px;
  color: var(--text-primary);
}

.toast.success {
  border-left: 4px solid var(--green);
}

.toast.error {
  border-left: 4px solid var(--red);
}

.toast.info {
  border-left: 4px solid var(--primary);
}

@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateX(40px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

/* ========== Modal ========== */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.4);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  animation: fadeIn 0.2s cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

.modal-content {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  padding: 32px;
  width: 500px;
  max-width: 90%;
  box-shadow: var(--shadow-lg);
  animation: modalIn 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

@keyframes modalIn {
  from {
    opacity: 0;
    transform: scale(0.95);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

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

.modal-confirm .modal-content {
  width: 420px;
}

.modal-confirm-actions {
  display: flex;
  gap: 12px;
  justify-content: flex-end;
  margin-top: 24px;
}

.modal-confirm-actions .btn {
  min-width: 88px;
}

.modal-content h3 {
  font-size: 17px;
  font-weight: 600;
  margin-bottom: 20px;
  letter-spacing: -0.02em;
}

/* ========== Student List (Teacher) ========== */
.student-table {
  width: 100%;
  border-collapse: collapse;
}

.student-table th,
.student-table td {
  padding: 12px 16px;
  text-align: left;
  border-bottom: 0.5px solid var(--separator);
  font-size: 14px;
}

.student-table th {
  background: var(--bg);
  font-weight: 600;
  color: var(--text-secondary);
  font-size: 13px;
}

.student-table tr:hover td {
  background: var(--fill);
}

.student-table .score-badge {
  display: inline-block;
  padding: 2px 10px;
  border-radius: 10px;
  font-size: 12px;
  font-weight: 600;
}

.score-badge.excellent {
  background: rgba(52, 199, 89, 0.1);
  color: var(--green);
}

.score-badge.good {
  background: rgba(0, 122, 255, 0.1);
  color: var(--primary);
}

.score-badge.average {
  background: rgba(255, 149, 0, 0.1);
  color: var(--orange);
}

.score-badge.poor {
  background: rgba(255, 59, 48, 0.1);
  color: var(--red);
}

/* ========== Mobile Header (Apple Frosted Glass) ========== */
.mobile-header {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 56px;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(40px) saturate(180%);
  -webkit-backdrop-filter: blur(40px) saturate(180%);
  color: var(--text-primary);
  align-items: center;
  justify-content: space-between;
  padding: 0 16px;
  z-index: 90;
  border-bottom: 0.5px solid var(--separator);
}

.mobile-header .menu-toggle {
  background: var(--fill);
  border: none;
  color: var(--text-primary);
  width: 38px;
  height: 38px;
  border-radius: 8px;
  font-size: 20px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0;
  transition: var(--transition);
}

.mobile-header .menu-toggle:active {
  background: rgba(120, 120, 128, 0.2);
  transform: scale(0.97);
  transition: transform 100ms ease-out;
}

.mobile-header .mobile-title {
  font-size: 16px;
  font-weight: 600;
  flex: 1;
  text-align: center;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.mobile-header .mobile-logout {
  padding: 0 12px;
  height: 38px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(255, 255, 255, 0.15);
  border: none;
  border-radius: 8px;
  color: var(--red, #ff3b30);
  font-size: 13px;
  cursor: pointer;
  font-weight: 500;
  white-space: nowrap;
}

.sidebar-overlay {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.3);
  z-index: 99;
  animation: fadeIn 0.2s cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

.sidebar-overlay.show {
  display: block;
}

.table-responsive {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

/* ========== Responsive ========== */
@media (max-width: 1200px) {
  .dashboard-grid {
    grid-template-columns: 1fr 1fr;
  }
  .dashboard-left {
    grid-column: 1 / -1;
  }
  .dashboard-center {
    grid-column: 1;
  }
  .dashboard-right {
    grid-column: 2;
  }
}

@media (max-width: 768px) {
  .kpi-row {
    grid-template-columns: 1fr 1fr;
    gap: 12px;
  }
  .dashboard-grid,
  .student-detail-grid {
    grid-template-columns: 1fr;
  }
  .dashboard-left,
  .dashboard-center,
  .dashboard-right {
    grid-column: 1;
  }

  /* Mobile header */
  .mobile-header {
    display: flex;
  }

  /* Sidebar becomes drawer */
  .sidebar {
    width: 240px;
    transform: translateX(-100%);
    transition: transform 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94);
    z-index: 100;
  }
  .sidebar.open {
    transform: translateX(0);
  }

  /* Main content full width */
  .main-content {
    margin-left: 0;
    padding: 16px 12px 24px;
    padding-top: 72px;
  }

  /* Page header */
  .page-header h1 {
    font-size: 22px;
    letter-spacing: -0.025em;
  }
  .page-header p {
    font-size: 13px;
  }

  /* KPI cards smaller */
  .kpi-card {
    padding: 14px 12px;
  }
  .kpi-card .kpi-value {
    font-size: 24px;
  }
  .kpi-card .kpi-label {
    font-size: 12px;
  }
  .kpi-card .kpi-icon {
    font-size: 24px;
  }

  /* Card spacing */
  .card-body {
    padding: 14px;
  }
  .card-header {
    padding: 12px 14px;
  }

  /* Chart container shorter */
  .chart-container {
    height: 220px;
  }

  /* Sidebar form sections */
  .sidebar-form-section h4 {
    font-size: 13px;
  }
  .counter-row {
    font-size: 12px;
    gap: 6px;
  }
  .counter-row .counter-label {
    width: 60px;
  }
  .score-input-row {
    font-size: 12px;
    gap: 6px;
  }
  .score-input-row .score-label {
    width: 44px;
  }
  .score-input-row input {
    width: 60px;
  }

  /* Tables scroll horizontally */
  .table-responsive {
    overflow-x: auto;
  }

  /* Upload zone smaller */
  .upload-zone {
    padding: 32px 20px;
  }
  .upload-zone .upload-icon {
    font-size: 36px;
  }
  .upload-zone h3 {
    font-size: 15px;
  }
  .upload-zone p {
    font-size: 13px;
  }

  /* Modal full width */
  .modal-content {
    width: 100%;
    max-width: 100%;
    padding: 20px 16px;
    border-radius: 14px;
  }

  /* Toast full width at bottom */
  .toast-container {
    top: auto;
    right: 0;
    left: 0;
    bottom: 16px;
    padding: 0 12px;
    align-items: stretch;
  }
  .toast {
    min-width: 0;
    width: 100%;
    font-size: 13px;
    padding: 12px 14px;
  }

  /* Student info bar stack */
  .student-info-bar {
    flex-direction: column;
    align-items: flex-start;
    gap: 12px;
    padding: 16px;
  }

  /* Score breakdown single column */
  .score-breakdown {
    grid-template-columns: 1fr;
  }

  /* Student charts grid single column */
  .student-charts-grid {
    grid-template-columns: 1fr;
  }

  /* Tabs scrollable */
  .tabs {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    white-space: nowrap;
    padding-bottom: 2px;
  }
  .tab-item {
    padding: 8px 16px;
    font-size: 13px;
    flex-shrink: 0;
  }

  /* Filter bar wrap */
  .filter-bar {
    flex-direction: column;
    align-items: stretch !important;
  }
  .filter-bar select,
  .filter-bar button {
    width: 100% !important;
    min-width: 0 !important;
  }

  /* Login card */
  .login-card {
    width: 100%;
    max-width: 92%;
    padding: 32px 24px;
    border-radius: 16px;
  }
  .login-card h1 {
    font-size: 22px;
  }
  .role-option {
    padding: 14px 8px;
  }
  .role-option .role-icon {
    font-size: 26px;
  }
  .role-option .role-label {
    font-size: 13px;
  }

  /* Big analysis score smaller */
  .analysis-score .big-score {
    font-size: 42px;
  }

  /* Student table denser */
  .student-table th,
  .student-table td {
    padding: 10px 10px;
    font-size: 13px;
  }
}

@media (max-width: 480px) {
  .main-content {
    padding: 12px 10px 20px;
    padding-top: 68px;
  }
  .kpi-row {
    grid-template-columns: 1fr;
    gap: 10px;
  }
  .kpi-card {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 14px;
  }
  .kpi-card .kpi-icon {
    font-size: 22px;
  }
  .kpi-card .kpi-value {
    font-size: 22px;
  }
  .login-card {
    padding: 24px 18px;
  }
  .role-selector {
    gap: 8px;
  }
}

/* ========== Back Button ========== */
.back-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--text-secondary);
  font-size: 14px;
  cursor: pointer;
  margin-bottom: 16px;
  transition: var(--transition);
  background: none;
  border: none;
  font-family: inherit;
}

.back-btn:hover {
  color: var(--primary);
}

.back-btn:active {
  transform: scale(0.97);
  transition: transform 100ms ease-out;
}

/* ========== Loading Spinner ========== */
.spinner {
  width: 40px;
  height: 40px;
  border: 3px solid var(--border);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  margin: 40px auto;
}

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

/* ========== Tabs ========== */
.tabs {
  display: flex;
  gap: 0;
  border-bottom: 0.5px solid var(--separator);
  margin-bottom: 20px;
}

.tab-item {
  padding: 10px 24px;
  font-size: 14px;
  color: var(--text-secondary);
  cursor: pointer;
  border-bottom: 2px solid transparent;
  margin-bottom: -0.5px;
  transition: var(--transition);
  background: none;
  border-top: none;
  border-left: none;
  border-right: none;
  font-family: inherit;
}

.tab-item:hover {
  color: var(--primary);
}

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

/* ========== Empty State ========== */
.empty-state {
  text-align: center;
  padding: 60px 20px;
  color: var(--text-secondary);
}

.empty-state .empty-icon {
  font-size: 48px;
  margin-bottom: 16px;
  opacity: 0.3;
}

.empty-state .empty-text {
  font-size: 15px;
  color: var(--text-secondary);
}

.empty-state h3 {
  font-size: 17px;
  margin-bottom: 8px;
  color: var(--text-primary);
}

/* ========== Error State ========== */
.error-state {
  text-align: center;
  padding: 60px 20px;
  color: var(--text-secondary);
}

.error-state .error-icon {
  font-size: 48px;
  margin-bottom: 16px;
  opacity: 0.5;
}

.error-state .error-text {
  font-size: 15px;
  color: var(--text-secondary);
  margin-bottom: 16px;
}

.error-state .btn-retry {
  display: inline-block;
  padding: 8px 20px;
  background: var(--primary);
  color: #fff;
  border: none;
  border-radius: 8px;
  font-size: 14px;
  cursor: pointer;
  transition: var(--transition);
}

.error-state .btn-retry:hover {
  background: var(--primary-dark);
}

/* ========== Global Loading Overlay ========== */
.global-loading {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(255,255,255,0.7);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  z-index: 9998;
  animation: fadeIn 0.2s ease;
}

.global-loading .loading-spinner {
  width: 36px;
  height: 36px;
  border: 3px solid var(--border);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

.global-loading .loading-text {
  margin-top: 16px;
  font-size: 14px;
  color: var(--text-secondary);
}

/* ========== Student Chart Grid ========== */
.student-charts-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  margin-top: 20px;
}

/* ========== Progress bar for upload ========== */
.upload-progress {
  width: 100%;
  height: 6px;
  background: var(--border);
  border-radius: 3px;
  margin-top: 12px;
  overflow: hidden;
  display: none;
}

.upload-progress.active {
  display: block;
}

.upload-progress .progress-fill {
  height: 100%;
  background: var(--primary);
  border-radius: 3px;
  transition: width 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

/* ========== Accessibility: Reduced Motion ========== */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
  }
}

/* ========== Accessibility: Reduced Transparency ========== */
@media (prefers-reduced-transparency: reduce) {
  .sidebar {
    background: #FFFFFF !important;
    backdrop-filter: none !important;
    -webkit-backdrop-filter: none !important;
  }
  .mobile-header {
    background: #FFFFFF !important;
    backdrop-filter: none !important;
    -webkit-backdrop-filter: none !important;
  }
  .toast {
    background: #FFFFFF !important;
    backdrop-filter: none !important;
    -webkit-backdrop-filter: none !important;
  }
}

/* ========== Accessibility: Increased Contrast ========== */
@media (prefers-contrast: more) {
  :root {
    --border: #333333;
    --text-secondary: #555555;
    --separator: rgba(0, 0, 0, 0.3);
    --fill: rgba(0, 0, 0, 0.08);
  }
}

/* ========== Shared UX Utilities ========== */
.empty-state { display:flex; flex-direction:column; align-items:center; justify-content:center; padding:48px 20px; color:var(--text-secondary); text-align:center; }
.empty-state-icon { font-size:40px; margin-bottom:12px; }
.empty-state-title { font-size:16px; font-weight:600; color:var(--text-primary); margin-bottom:6px; }
.empty-state-subtitle { font-size:13px; color:var(--text-secondary); }
.empty-state .empty-action { margin-top:14px; }

.global-loading { display:flex; align-items:center; justify-content:center; gap:10px; padding:24px; color:var(--text-secondary); }
.loading-spinner { width:18px; height:18px; border:2px solid var(--fill); border-top-color:var(--primary); border-radius:50%; animation:spin .8s linear infinite; }
.loading-text { font-size:13px; }
@keyframes spin { to { transform: rotate(360deg); } }

.upload-drop-zone { border:2px dashed var(--border); border-radius:var(--radius); padding:28px 20px; text-align:center; background:var(--card-bg); transition:var(--transition); cursor:pointer; }
.upload-drop-zone:hover, .upload-drop-zone.dragover { border-color:var(--primary); background:rgba(0,122,255,0.04); }
.upload-drop-zone[tabindex="0"]:focus { outline:none; border-color:var(--primary); box-shadow:0 0 0 3px rgba(0,122,255,0.15); }
.upload-drop-zone .upload-icon { font-size:32px; margin-bottom:8px; }
.upload-drop-zone .upload-title { font-size:15px; font-weight:600; color:var(--text-primary); }
.upload-drop-zone .upload-hint { font-size:13px; color:var(--text-secondary); margin-top:4px; }

.action-row { display:flex; gap:10px; flex-wrap:wrap; }
.action-row .btn-back { border-radius:var(--radius-sm); padding:8px 16px; font-size:14px; }

.modal-close-btn { width:32px; height:32px; border-radius:50%; background:var(--fill); border:none; cursor:pointer; font-size:18px; display:inline-flex; align-items:center; justify-content:center; transition:var(--transition); }
.modal-close-btn:hover { background:var(--separator); }

.field-error { border-color:var(--red) !important; box-shadow:0 0 0 3px rgba(255,59,48,0.12) !important; }
.field-error-text { font-size:12px; color:var(--red); margin-top:6px; }

.segmented-control { display:inline-flex; gap:8px; padding:4px; background:var(--fill); border-radius:var(--radius-sm); }
.segmented-control .segmented-btn { border:none; background:transparent; padding:8px 14px; border-radius:8px; font-size:14px; color:var(--text-secondary); cursor:pointer; transition:var(--transition); }
.segmented-control .segmented-btn.active { background:var(--card-bg); color:var(--text-primary); box-shadow:var(--shadow-sm); }
.segmented-control .segmented-btn:not(.active):hover { color:var(--text-primary); }