:root {
  --bg-primary: #0b0f19;
  --bg-surface: #111827;
  --bg-card: #162032;
  --bg-hover: #1e2c45;
  --bg-active: #253754;
  
  --border-color: rgba(255, 255, 255, 0.08);
  --border-highlight: rgba(255, 255, 255, 0.16);
  
  --text-main: #f8fafc;
  --text-muted: #94a3b8;
  --text-dim: #64748b;
  
  --primary: #3b82f6;
  --primary-hover: #2563eb;
  --primary-light: rgba(59, 130, 246, 0.14);
  
  --success: #10b981;
  --success-bg: rgba(16, 185, 129, 0.14);
  --warning: #f59e0b;
  --warning-bg: rgba(245, 158, 11, 0.14);
  --danger: #ef4444;
  --danger-bg: rgba(239, 68, 68, 0.14);
  
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", monospace;
  
  --radius-sm: 6px;
  --radius: 10px;
  --radius-lg: 14px;
  
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
  --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.35), 0 2px 4px -2px rgba(0, 0, 0, 0.25);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.5), 0 4px 6px -4px rgba(0, 0, 0, 0.3);
}

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

body {
  font-family: var(--font-family);
  background-color: var(--bg-primary);
  color: var(--text-main);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Base Layout */
.app-container {
  display: flex;
  min-height: 100vh;
}

/* Sidebar */
.sidebar {
  width: 260px;
  background-color: var(--bg-surface);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  padding: 1.25rem 0.85rem;
  flex-shrink: 0;
}

.sidebar-header {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  margin-bottom: 1.25rem;
  padding: 0.25rem 0.5rem 1rem 0.5rem;
  border-bottom: 1px solid var(--border-color);
}

.brand-icon {
  background: linear-gradient(135deg, #3b82f6, #1d4ed8);
  color: #ffffff;
  width: 38px;
  height: 38px;
  border-radius: 9px;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 2px 6px rgba(59, 130, 246, 0.35);
  flex-shrink: 0;
}

.brand-text {
  display: flex;
  flex-direction: column;
}

.brand-title {
  font-size: 1.15rem;
  font-weight: 700;
  letter-spacing: -0.015em;
  color: var(--text-main);
  line-height: 1.2;
}

.brand-subtitle {
  font-size: 0.72rem;
  color: var(--text-dim);
  font-weight: 500;
  letter-spacing: 0.02em;
}

.nav-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
  flex: 1;
}

.nav-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.65rem 0.85rem;
  border-radius: var(--radius-sm);
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.88rem;
  font-weight: 500;
  cursor: pointer;
  user-select: none;
  transition: all 0.15s cubic-bezier(0.4, 0, 0.2, 1);
  border-left: 3px solid transparent;
}

.nav-item:hover {
  background-color: var(--bg-hover);
  color: var(--text-main);
  transform: translateX(2px);
}

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

.nav-item-separator {
  height: 1px;
  background-color: var(--border-color);
  margin: 0.6rem 0.5rem;
}

.nav-item-logout {
  color: var(--danger) !important;
}

.nav-item-logout:hover {
  background-color: var(--danger-bg) !important;
  color: var(--danger) !important;
}

.nav-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 20px;
  height: 20px;
  flex-shrink: 0;
}

/* Main Content Wrapper */
.main-wrapper {
  flex: 1;
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  background-color: var(--bg-primary);
}

.topbar {
  background-color: rgba(17, 24, 39, 0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-color);
  padding: 0.85rem 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  position: sticky;
  top: 0;
  z-index: 50;
}

.topbar-title {
  font-size: 1.15rem;
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--text-main);
}

.topbar-actions {
  display: flex;
  gap: 0.6rem;
  align-items: center;
}

.content-area {
  padding: 2rem;
  flex: 1;
  max-width: 1400px;
  width: 100%;
  margin: 0 auto;
}

/* Grids */
.grid-2 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 1.25rem;
  margin-bottom: 1.25rem;
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.25rem;
  margin-bottom: 1.25rem;
}

/* Cards */
.card {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: var(--shadow);
  transition: border-color 0.15s ease;
}

.card:hover {
  border-color: var(--border-highlight);
}

.card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
}

.card-title {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text-main);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  letter-spacing: -0.01em;
}

/* Badges & Metrics */
.metric-box {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  position: relative;
}

.metric-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
}

.metric-icon-wrap {
  width: 32px;
  height: 32px;
  border-radius: 8px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.metric-icon-wrap .svg-icon {
  width: 16px;
  height: 16px;
}

.metric-icon-accent {
  background: rgba(59, 130, 246, 0.12);
  color: var(--primary);
  border: 1px solid rgba(59, 130, 246, 0.25);
}

.metric-icon-success {
  background: rgba(16, 185, 129, 0.12);
  color: var(--success);
  border: 1px solid rgba(16, 185, 129, 0.25);
}

.metric-icon-warning {
  background: rgba(245, 158, 11, 0.12);
  color: var(--warning);
  border: 1px solid rgba(245, 158, 11, 0.25);
}

.metric-icon-danger {
  background: rgba(239, 68, 68, 0.12);
  color: var(--danger);
  border: 1px solid rgba(239, 68, 68, 0.25);
}

.metric-val {
  font-size: 1.95rem;
  font-weight: 700;
  color: var(--text-main);
  letter-spacing: -0.025em;
  font-variant-numeric: tabular-nums;
  line-height: 1.15;
}

.metric-val-max {
  font-size: 1.15rem;
  font-weight: 500;
  color: var(--text-muted);
}

.metric-label {
  font-size: 0.8rem;
  color: var(--text-muted);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.035em;
}

.metric-sub {
  font-size: 0.8rem;
  color: var(--text-dim);
  font-weight: 500;
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.25rem 0.6rem;
  border-radius: 6px;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.01em;
  white-space: nowrap;
}

.badge-primary {
  background-color: var(--primary-light);
  color: var(--primary);
  border: 1px solid rgba(59, 130, 246, 0.25);
}

.badge-success {
  background-color: var(--success-bg);
  color: var(--success);
  border: 1px solid rgba(16, 185, 129, 0.25);
}

.badge-warning {
  background-color: var(--warning-bg);
  color: var(--warning);
  border: 1px solid rgba(245, 158, 11, 0.25);
}

.badge-danger {
  background-color: var(--danger-bg);
  color: var(--danger);
  border: 1px solid rgba(239, 68, 68, 0.25);
}

.badge-secondary {
  background-color: rgba(255, 255, 255, 0.06);
  color: var(--text-muted);
  border: 1px solid var(--border-color);
}

.badge-sm {
  padding: 0.15rem 0.45rem;
  font-size: 0.7rem;
}

/* Buttons - 8-State Interactive Feedback Standard */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.45rem;
  padding: 0.55rem 1rem;
  border-radius: var(--radius-sm);
  font-size: 0.88rem;
  font-weight: 600;
  cursor: pointer;
  border: 1px solid transparent;
  user-select: none;
  transition: background-color 140ms ease-out, border-color 140ms ease-out, transform 80ms ease-out, box-shadow 140ms ease-out;
  min-height: 40px;
}

.btn:active {
  transform: scale(0.97);
}

.btn:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

.btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
  pointer-events: none;
}

.btn-primary {
  background-color: var(--primary);
  color: #ffffff;
  box-shadow: 0 1px 3px rgba(59, 130, 246, 0.3);
}

.btn-primary:hover {
  background-color: var(--primary-hover);
  box-shadow: 0 2px 6px rgba(59, 130, 246, 0.4);
}

.btn-secondary {
  background-color: var(--bg-card);
  color: var(--text-main);
  border: 1px solid var(--border-color);
}

.btn-secondary:hover {
  background-color: var(--bg-hover);
  border-color: var(--border-highlight);
}

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

.btn-success:hover {
  background-color: #059669;
}

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

.btn-danger:hover {
  background-color: #dc2626;
}

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

.btn-ghost:hover {
  background-color: var(--bg-hover);
  color: var(--text-main);
}

.btn-logout-top {
  color: var(--danger);
  border: 1px solid rgba(239, 68, 68, 0.25);
}

.btn-logout-top:hover {
  background-color: var(--danger-bg);
  color: var(--danger);
  border-color: var(--danger);
}

.btn-sm {
  padding: 0.35rem 0.75rem;
  font-size: 0.8rem;
  min-height: 32px;
  gap: 0.35rem;
}

.btn-sm .svg-icon {
  width: 14px;
  height: 14px;
}

.btn-icon {
  display: inline-flex;
  stroke-width: 2px;
  flex-shrink: 0;
}

/* Forms */
.form-group {
  margin-bottom: 1.15rem;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

label {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-muted);
  letter-spacing: 0.01em;
}

input, select, textarea {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 0.65rem 0.85rem;
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  font-family: inherit;
  width: 100%;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

input:focus, select:focus, textarea:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-light);
}

textarea {
  resize: vertical;
}

/* Tables */
table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.85rem;
  font-variant-numeric: tabular-nums;
}

th {
  padding: 0.75rem 1rem;
  background-color: rgba(255, 255, 255, 0.02);
  color: var(--text-muted);
  font-weight: 600;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  border-bottom: 1px solid var(--border-color);
  text-align: left;
}

td {
  padding: 0.85rem 1rem;
  border-bottom: 1px solid var(--border-color);
  color: var(--text-main);
}

tbody tr {
  transition: background-color 0.1s ease;
}

tbody tr:hover {
  background-color: rgba(255, 255, 255, 0.02);
}

/* Test Runner UI */
.test-runner-container {
  max-width: 860px;
  margin: 0 auto;
}

.test-progress-bar {
  height: 6px;
  background-color: rgba(255, 255, 255, 0.08);
  border-radius: 9999px;
  overflow: hidden;
  margin-bottom: 1.25rem;
}

.test-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, #3b82f6, #60a5fa);
  transition: width 0.25s ease;
  border-radius: 9999px;
}

.question-card {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  padding: 2rem;
  margin-bottom: 1.5rem;
  box-shadow: var(--shadow);
}

.question-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.25rem;
}

.question-text {
  font-size: 1.1rem;
  font-weight: 500;
  line-height: 1.6;
  margin-bottom: 1.75rem;
  white-space: pre-wrap;
  color: var(--text-main);
}

.options-list {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  margin-bottom: 1.75rem;
}

.option-item {
  display: flex;
  align-items: flex-start;
  gap: 0.9rem;
  padding: 0.85rem 1.15rem;
  background-color: var(--bg-card);
  border: 1.5px solid var(--border-color);
  border-radius: var(--radius);
  cursor: pointer;
  transition: all 0.15s ease;
}

.option-item:hover {
  background-color: var(--bg-hover);
  border-color: var(--border-highlight);
}

.option-item.selected {
  border-color: var(--primary);
  background-color: var(--primary-light);
}

.option-item.correct {
  border-color: var(--success);
  background-color: var(--success-bg);
}

.option-item.incorrect {
  border-color: var(--danger);
  background-color: var(--danger-bg);
}

.option-id {
  font-weight: 700;
  background-color: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border-color);
  width: 28px;
  height: 28px;
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  font-size: 0.82rem;
  color: var(--text-main);
}

.option-text {
  font-size: 0.95rem;
  line-height: 1.5;
  color: var(--text-main);
  padding-top: 2px;
}

.explanation-box {
  background-color: var(--bg-card);
  border-left: 3px solid var(--primary);
  padding: 1rem 1.25rem;
  border-radius: 4px;
  margin-top: 1.25rem;
  font-size: 0.9rem;
  line-height: 1.55;
}

.test-nav-actions {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.75rem;
  margin-top: 1.5rem;
  flex-wrap: wrap;
}

.status-dot {
  display: inline-block;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  margin-right: 0.5rem;
  flex-shrink: 0;
}

.test-shortcuts {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  font-size: 0.78rem;
  color: var(--text-dim);
  text-align: center;
  margin-top: 1rem;
  flex-wrap: wrap;
}

kbd {
  display: inline-flex;
  align-items: center;
  padding: 0.15rem 0.45rem;
  background-color: rgba(255, 255, 255, 0.07);
  border: 1px solid rgba(255, 255, 255, 0.15);
  border-radius: 4px;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--text-main);
  box-shadow: 0 1px 1px rgba(0, 0, 0, 0.3);
}

/* SVG Icons & Vector Helpers */
.svg-icon {
  display: inline-flex;
  vertical-align: middle;
  stroke-width: 2px;
  flex-shrink: 0;
  width: 18px;
  height: 18px;
}

.icon-warning {
  color: var(--warning);
}

.icon-success {
  color: var(--success);
}

.icon-danger {
  color: var(--danger);
}

.icon-accent {
  color: var(--primary);
}

.icon-gold {
  color: #f59e0b;
}

.icon-muted {
  color: var(--text-dim);
}

.icon-info {
  color: var(--primary);
}

/* Star Ratings */
.stars-rating {
  display: inline-flex;
  align-items: center;
  gap: 2px;
  vertical-align: middle;
}

.star-icon {
  width: 15px;
  height: 15px;
}

.star-filled {
  color: #f59e0b;
  fill: #f59e0b;
}

.star-empty {
  color: rgba(255, 255, 255, 0.2);
  stroke: rgba(255, 255, 255, 0.25);
}

/* Modals */
.modal-overlay {
  position: fixed;
  inset: 0;
  background-color: rgba(9, 13, 22, 0.82);
  backdrop-filter: blur(8px);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
  z-index: 1000;
}

.modal-content {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-highlight);
  border-radius: var(--radius-lg);
  max-width: 600px;
  width: 100%;
  max-height: 90vh;
  overflow-y: auto;
  padding: 1.75rem 2rem;
  box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.7);
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.25rem;
}

.modal-title {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-main);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.modal-close-btn {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  padding: 0.35rem;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 6px;
  transition: color 0.15s ease, background 0.15s ease;
}

.modal-close-btn:hover {
  color: var(--text-main);
  background-color: var(--bg-hover);
}

/* Login Modal Specific */
.login-brand-icon {
  display: inline-flex;
  width: 52px;
  height: 52px;
  background: linear-gradient(135deg, #3b82f6, #1d4ed8);
  border-radius: 12px;
  align-items: center;
  justify-content: center;
  color: #ffffff;
  margin-bottom: 0.75rem;
  box-shadow: 0 4px 12px rgba(59, 130, 246, 0.35);
}

.login-brand-icon .svg-icon {
  width: 24px;
  height: 24px;
}

/* Informational banners */
.balancing-banner {
  font-size: 0.82rem;
  background: var(--bg-surface);
  padding: 0.6rem 0.85rem;
  border-radius: 6px;
  margin-bottom: 1rem;
  color: var(--text-muted);
  border-left: 3px solid var(--primary);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

/* Responsive Breakpoints */
@media (max-width: 900px) {
  .app-container {
    flex-direction: column;
  }
  .sidebar {
    width: 100%;
    border-right: none;
    border-bottom: 1px solid var(--border-color);
    padding: 0.75rem 1rem;
  }
  .sidebar-header {
    margin-bottom: 0.75rem;
    padding-bottom: 0.5rem;
  }
  .nav-links {
    flex-direction: row;
    overflow-x: auto;
    padding-bottom: 0.5rem;
    gap: 0.35rem;
  }
  .nav-item-separator {
    display: none;
  }
  .nav-item {
    white-space: nowrap;
    padding: 0.5rem 0.75rem;
    font-size: 0.82rem;
    border-left: none;
    border-bottom: 2px solid transparent;
  }
  .nav-item.active {
    border-left-color: transparent;
    border-bottom-color: var(--primary);
  }
  .topbar {
    padding: 0.75rem 1rem;
  }
  .content-area {
    padding: 1rem;
  }
}

@media (max-width: 640px) {
  .topbar {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.65rem;
    padding: 0.75rem 1rem;
  }
  .topbar-title {
    font-size: 1.05rem;
  }
  .topbar-actions {
    width: 100%;
    flex-wrap: wrap;
    gap: 0.4rem;
  }
  .grid-2, .grid-3 {
    grid-template-columns: 1fr;
    gap: 1rem;
  }
  .content-area {
    padding: 0.85rem;
  }
  .question-card {
    padding: 1.25rem 1rem;
  }
  .test-nav-actions {
    flex-direction: column;
  }
  .test-nav-actions .btn {
    width: 100%;
  }
  .modal-content {
    padding: 1.25rem;
    margin: 0.5rem;
  }
}