:root {
  --bg: #0a0e1a;
  --bg-secondary: #0f1525;
  --card: #151b2e;
  --card-hover: #1a2137;
  --text: #ffffff;
  --text-secondary: #e5e7eb;
  --text-muted: #9ca3af;
  --accent: #5b8ef5;
  --accent-hover: #4a7de4;
  --accent-light: rgba(91, 142, 245, 0.15);
  --ok: #10b981;
  --ok-light: rgba(16, 185, 129, 0.15);
  --bad: #ef4444;
  --bad-light: rgba(239, 68, 68, 0.15);
  --border: rgba(255, 255, 255, 0.08);
  --border-hover: rgba(255, 255, 255, 0.15);
  --shadow: rgba(0, 0, 0, 0.3);
  --gradient-1: #1e3a8a;
  --gradient-2: #7c3aed;
}

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

body {
  margin: 0;
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

.bg-gradient {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: 
    radial-gradient(circle at 20% 10%, rgba(91, 142, 245, 0.15) 0%, transparent 50%),
    radial-gradient(circle at 80% 80%, rgba(124, 58, 237, 0.12) 0%, transparent 50%),
    radial-gradient(circle at 40% 60%, rgba(16, 185, 129, 0.08) 0%, transparent 40%);
  pointer-events: none;
  z-index: 0;
}

.app {
  position: relative;
  z-index: 1;
  width: 100%;
  max-width: 1540px;
  margin: 0 auto;
  padding: 0 24px 24px;
}

/* Topbar */
.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 0;
  margin-bottom: 12px;
  gap: 16px;
}

.topbar-left {
  display: flex;
  align-items: center;
  gap: 16px;
  flex: 1;
}

.topbar-right {
  display: flex;
  align-items: center;
  gap: 12px;
}

.iconbtn {
  display: none;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border: 1px solid var(--border);
  background: rgba(21, 27, 46, 0.6);
  backdrop-filter: blur(12px);
  color: var(--text);
  border-radius: 14px;
  cursor: pointer;
  transition: all 0.2s ease;
}

.iconbtn:hover {
  border-color: var(--border-hover);
  background: rgba(21, 27, 46, 0.8);
  transform: translateY(-1px);
}

.iconbtn:active {
  transform: translateY(0);
}

.logo {
  display: flex;
  align-items: center;
  gap: 12px;
}

.logo-icon {
  filter: drop-shadow(0 4px 12px rgba(91, 142, 245, 0.3));
}

.topbar h1 {
  margin: 0;
  font-size: 26px;
  font-weight: 800;
  letter-spacing: -0.02em;
  background: linear-gradient(135deg, var(--text) 0%, var(--text-secondary) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.meta-item {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 16px;
  background: rgba(21, 27, 46, 0.5);
  backdrop-filter: blur(12px);
  border: 1px solid var(--border);
  border-radius: 12px;
  color: var(--text-secondary);
  font-size: 14px;
  font-weight: 600;
  white-space: nowrap;
  transition: all 0.2s ease;
}

.meta-item svg {
  opacity: 0.7;
}

.meta-score {
  background: linear-gradient(135deg, rgba(91, 142, 245, 0.3) 0%, rgba(124, 58, 237, 0.25) 100%);
  border: 2px solid rgba(91, 142, 245, 0.5);
  color: var(--text);
  width: 185px;
  justify-content: center;
}

.meta-score svg {
  opacity: 1;
  color: #fbbf24;
  filter: drop-shadow(0 2px 6px rgba(251, 191, 36, 0.5));
}

/* Layout */
.layout {
  display: flex;
  gap: 16px;
  align-items: flex-start;
}

/* Legend Panel (Right Sidebar) */
.sidebar-right {
  width: 185px;
  flex: 0 0 185px;
  position: sticky;
  top: 16px;
}

.legend-panel {
  border: 1px solid var(--border);
  border-radius: 16px;
  background: rgba(21, 27, 46, 0.5);
  backdrop-filter: blur(20px);
  padding: 16px;
  box-shadow: 
    0 10px 30px rgba(0, 0, 0, 0.2),
    inset 0 1px 0 rgba(255, 255, 255, 0.1);
}

.legend-title {
  font-size: 14px;
  font-weight: 700;
  color: var(--text-secondary);
  margin: 0 0 14px 0;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--border);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.legend-items {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 10px;
}

.legend-label {
  font-size: 13px;
  color: var(--text-muted);
  font-weight: 500;
}

.legend-dot {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  border: 2px solid var(--border);
  background: rgba(255, 255, 255, 0.08);
  flex-shrink: 0;
}

.legend-dot.legend-ok {
  background: var(--ok);
  border-color: var(--ok);
  box-shadow: 0 0 8px rgba(16, 185, 129, 0.4);
}

.legend-dot.legend-bad {
  background: var(--bad);
  border-color: var(--bad);
  box-shadow: 0 0 8px rgba(239, 68, 68, 0.4);
}

.sidebar-info {
  margin-top: 16px;
  padding: 16px;
  border: 1px solid var(--border);
  border-radius: 16px;
  background: rgba(21, 27, 46, 0.5);
  backdrop-filter: blur(20px);
  box-shadow:
    0 10px 30px rgba(0, 0, 0, 0.2),
    inset 0 1px 0 rgba(255, 255, 255, 0.1);
}

.sidebar-desc {
  font-size: 13px;
  line-height: 1.7;
  color: var(--text-secondary);
  font-weight: 500;
  margin: 0 0 14px 0;
  padding-bottom: 14px;
  border-bottom: 1px solid var(--border);
}

.sidebar-desc strong {
  color: var(--accent);
  font-weight: 700;
}

.sidebar-credit {
  font-size: 12px;
  font-weight: 500;
  color: var(--text-secondary);
  text-align: center;
  margin: 0;
}

.sidebar-credit strong {
  color: var(--text);
  font-weight: 600;
}

/* Sidebar */
.sidebar {
  width: 275px;
  flex: 0 0 275px;
  position: sticky;
  top: 16px;
  max-height: calc(100vh - 100px);
  overflow: hidden;
  border: 1px solid var(--border);
  border-radius: 16px;
  background: rgba(21, 27, 46, 0.5);
  backdrop-filter: blur(20px);
  box-shadow: 
    0 20px 50px rgba(0, 0, 0, 0.3),
    inset 0 1px 0 rgba(255, 255, 255, 0.1);
}

.sidebar-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 14px 14px;
  border-top: 1px solid rgba(91, 142, 245, 0.15);
  border-bottom: 1px solid rgba(91, 142, 245, 0.2);
  border-radius: 16px 16px 0 0;
  background: linear-gradient(135deg, rgba(91, 142, 245, 0.08) 0%, rgba(124, 58, 237, 0.05) 100%);
  position: relative;
}

.sidebar-head::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, rgba(91, 142, 245, 0.4), transparent);
}

.sidebar-title {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 800;
  font-size: 14px;
  letter-spacing: -0.02em;
  color: var(--text);
  text-transform: uppercase;
}

.sidebar-title svg {
  opacity: 0.8;
  color: var(--accent);
  filter: drop-shadow(0 2px 4px rgba(91, 142, 245, 0.3));
}

.sidebar-sub {
  color: var(--text-secondary);
  font-weight: 700;
  font-size: 13px;
  padding: 6px 12px;
  background: rgba(91, 142, 245, 0.15);
  border: 1px solid rgba(91, 142, 245, 0.3);
  border-radius: 10px;
  box-shadow: 0 2px 8px rgba(91, 142, 245, 0.2);
}

.sidebar-list {
  padding: 8px;
  overflow-y: auto;
  overflow-x: hidden;
  max-height: calc(100vh - 100px - 52px);
  display: grid;
  gap: 4px;
}

.sidebar-list::-webkit-scrollbar {
  width: 6px;
}

.sidebar-list::-webkit-scrollbar-track {
  background: transparent;
}

.sidebar-list::-webkit-scrollbar-thumb {
  background: rgba(255, 255, 255, 0.1);
  border-radius: 10px;
}

.sidebar-list::-webkit-scrollbar-thumb:hover {
  background: rgba(255, 255, 255, 0.15);
}

.qitem {
  display: flex;
  align-items: center;
  gap: 8px;
  width: 100%;
  border: 1px solid var(--border);
  background: rgba(21, 27, 46, 0.6);
  color: var(--text);
  border-radius: 10px;
  padding: 8px;
  cursor: pointer;
  text-align: left;
  transition: all 0.2s ease;
  position: relative;
  overflow: hidden;
}

.qitem::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(135deg, rgba(91, 142, 245, 0.1) 0%, transparent 100%);
  opacity: 0;
  transition: opacity 0.2s ease;
}

.qitem:hover {
  border-color: var(--accent);
  background: rgba(26, 33, 55, 0.8);
  transform: translateX(4px);
}

.qitem:hover::before {
  opacity: 1;
}

.qitem.active {
  border-color: var(--accent);
  background: var(--accent-light);
  box-shadow: 
    0 0 0 3px rgba(91, 142, 245, 0.1),
    0 8px 20px rgba(91, 142, 245, 0.2);
}

.qitem.active::before {
  opacity: 1;
}

.qnum {
  width: 32px;
  height: 26px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  font-weight: 800;
  font-size: 11px;
  flex: 0 0 auto;
  transition: all 0.2s ease;
}

.qitem:hover .qnum {
  background: rgba(91, 142, 245, 0.15);
  border-color: var(--accent);
  color: var(--accent);
}

.qitem.active .qnum {
  background: var(--accent);
  border-color: var(--accent);
  color: white;
  box-shadow: 0 4px 12px rgba(91, 142, 245, 0.4);
}

.qstatus {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  border: 2px solid var(--border);
  background: rgba(255, 255, 255, 0.08);
  flex: 0 0 auto;
  transition: all 0.2s ease;
}

.qstatus.ok {
  background: var(--ok);
  border-color: var(--ok);
  box-shadow: 0 0 12px rgba(16, 185, 129, 0.5);
}

.qstatus.bad {
  background: var(--bad);
  border-color: var(--bad);
  box-shadow: 0 0 12px rgba(239, 68, 68, 0.5);
}

.qtext {
  flex: 1 1 auto;
  color: var(--text-secondary);
  font-weight: 600;
  font-size: 12px;
  line-height: 1.4;
  overflow: hidden;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
}

.qitem:hover .qtext {
  color: var(--text);
}

.qitem.active .qtext {
  color: var(--text);
}

/* Content */
.content {
  flex: 1 1 auto;
  min-width: 0;
}

.card {
  background: rgba(21, 27, 46, 0.5);
  backdrop-filter: blur(20px);
  border: 1px solid var(--border);
  border-radius: 20px;
  padding: 20px 24px;
  box-shadow: 
    0 20px 50px rgba(0, 0, 0, 0.3),
    inset 0 1px 0 rgba(255, 255, 255, 0.1);
  animation: cardFadeIn 0.4s ease;
}

@keyframes cardFadeIn {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Slide transitions for question change */
@keyframes slideInRight {
  from {
    opacity: 0;
    transform: translateX(50px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

@keyframes slideInLeft {
  from {
    opacity: 0;
    transform: translateX(-50px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

.card.slide-right .question,
.card.slide-right .answers,
.card.slide-right .feedback {
  animation: slideInRight 0.3s cubic-bezier(0.22, 1, 0.36, 1);
}

.card.slide-left .question,
.card.slide-left .answers,
.card.slide-left .feedback {
  animation: slideInLeft 0.3s cubic-bezier(0.22, 1, 0.36, 1);
}

.question-header {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-bottom: 14px;
}

.tag {
  display: inline-flex;
  align-items: center;
  height: 32px;
  padding: 0 14px;
  border-radius: 10px;
  background: linear-gradient(135deg, var(--accent-light) 0%, rgba(124, 58, 237, 0.1) 100%);
  border: 1px solid rgba(91, 142, 245, 0.3);
  color: var(--accent);
  font-weight: 700;
  font-size: 13px;
  letter-spacing: 0.02em;
  text-transform: uppercase;
  flex-shrink: 0;
}

.progress-bar {
  flex: 1;
  height: 6px;
  background: rgba(255, 255, 255, 0.06);
  border-radius: 10px;
  overflow: hidden;
  position: relative;
}

.progress-percent {
  font-size: 13px;
  font-weight: 700;
  color: var(--accent);
  min-width: 42px;
  text-align: right;
  flex-shrink: 0;
  font-variant-numeric: tabular-nums;
  transition: color 0.3s ease;
}

.progress-percent.complete {
  color: var(--ok);
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent) 0%, var(--gradient-2) 100%);
  border-radius: 10px;
  transition: width 0.4s cubic-bezier(0.4, 0, 0.2, 1);
  box-shadow: 0 0 20px rgba(91, 142, 245, 0.5);
  position: relative;
  overflow: hidden;
}

.progress-fill::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.3), transparent);
  animation: shimmer 2s infinite;
}

@keyframes shimmer {
  0% { transform: translateX(-100%); }
  100% { transform: translateX(100%); }
}

.question h2 {
  margin: 0;
  font-size: 19px;
  font-weight: 700;
  line-height: 1.4;
  color: var(--text);
  letter-spacing: -0.01em;
}

.hint {
  margin: 10px 0 0;
  color: var(--text-muted);
  font-size: 14px;
  line-height: 1.5;
  padding: 10px 14px;
  background: rgba(255, 255, 255, 0.03);
  border-left: 3px solid rgba(91, 142, 245, 0.3);
  border-radius: 8px;
}

/* Answers */
.answers {
  margin-top: 16px;
  display: grid;
  gap: 10px;
}

.answer {
  background: rgba(21, 27, 46, 0.6);
  border: 2px solid var(--border);
  padding: 14px 16px;
  border-radius: 14px;
  cursor: pointer;
  transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  color: var(--text);
  text-align: left;
  font-size: 15px;
  font-weight: 500;
  line-height: 1.4;
  position: relative;
  overflow: hidden;
}

.answer::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(135deg, rgba(91, 142, 245, 0.1) 0%, transparent 100%);
  opacity: 0;
  transition: opacity 0.2s ease;
}

.answer:hover {
  transform: translateY(-2px);
  border-color: var(--accent);
  background: rgba(26, 33, 55, 0.8);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.2);
}

.answer:hover::before {
  opacity: 1;
}

.answer:active {
  transform: translateY(0);
}

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

.answer.selected {
  border-color: var(--accent);
  background: var(--accent-light);
  box-shadow: 
    0 0 0 3px rgba(91, 142, 245, 0.15),
    0 8px 24px rgba(91, 142, 245, 0.25);
}

.answer.selected::before {
  opacity: 1;
}

.answer.correct {
  border-color: var(--ok);
  background: var(--ok-light);
  box-shadow: 
    0 0 0 3px rgba(16, 185, 129, 0.15),
    0 8px 24px rgba(16, 185, 129, 0.25);
}

.answer.correct::before {
  background: linear-gradient(135deg, rgba(16, 185, 129, 0.15) 0%, transparent 100%);
  opacity: 1;
}

.answer.wrong {
  border-color: var(--bad);
  background: var(--bad-light);
  box-shadow: 
    0 0 0 3px rgba(239, 68, 68, 0.15),
    0 8px 24px rgba(239, 68, 68, 0.25);
}

.answer.wrong::before {
  background: linear-gradient(135deg, rgba(239, 68, 68, 0.15) 0%, transparent 100%);
  opacity: 1;
}

/* Feedback */
.feedback {
  margin-top: 16px;
  padding: 14px 16px;
  border-radius: 14px;
  border: 1px solid var(--border);
  background: rgba(21, 27, 46, 0.4);
  color: var(--text-secondary);
  min-height: 50px;
  line-height: 1.5;
  font-size: 14px;
  animation: fadeIn 0.3s ease;
}

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

/* Actions */
.actions {
  margin-top: 16px;
  display: flex;
  gap: 10px;
  justify-content: flex-end;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  border: none;
  background: var(--accent);
  color: white;
  font-weight: 700;
  font-size: 14px;
  padding: 10px 18px;
  border-radius: 12px;
  cursor: pointer;
  transition: all 0.2s ease;
  box-shadow: 0 4px 12px rgba(91, 142, 245, 0.3);
  position: relative;
  overflow: hidden;
}

.btn::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(135deg, rgba(255, 255, 255, 0.2) 0%, transparent 100%);
  opacity: 0;
  transition: opacity 0.2s ease;
}

.btn:hover {
  background: var(--accent-hover);
  transform: translateY(-2px);
  box-shadow: 0 8px 20px rgba(91, 142, 245, 0.4);
}

.btn:hover::before {
  opacity: 1;
}

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

.btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

.btn:disabled:hover {
  background: var(--accent);
  transform: none;
}

.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border);
  box-shadow: none;
}

.btn-ghost:hover {
  background: rgba(255, 255, 255, 0.05);
  border-color: var(--border-hover);
  color: var(--text);
  box-shadow: none;
}

.btn-ghost:disabled {
  opacity: 0.4;
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent) 0%, var(--gradient-2) 100%);
}

.btn-primary:hover {
  background: linear-gradient(135deg, var(--accent-hover) 0%, #6d28d9 100%);
}

/* Footer */
.footer {
  margin-top: 16px;
  padding: 12px 16px;
  background: rgba(21, 27, 46, 0.3);
  border: 1px solid var(--border);
  border-radius: 14px;
  color: var(--text-muted);
  text-align: center;
}

.footer small {
  font-size: 12px;
  display: block;
  line-height: 1.5;
}

/* Mobile */
@media (max-width: 1024px) {
  .app {
    padding: 0 20px 32px;
  }

  .iconbtn {
    display: inline-flex;
  }

  .topbar {
    padding: 20px 0;
  }

  .topbar h1 {
    font-size: 22px;
  }

  .topbar-left {
    flex: 1;
  }

  .topbar-right {
    gap: 8px;
  }

  .layout {
    flex-direction: column;
    gap: 16px;
  }

  .sidebar-right {
    display: none;
  }

  .sidebar {
    position: fixed;
    top: 88px;
    left: 20px;
    right: 20px;
    width: auto;
    max-height: 70vh;
    transform: translateY(-150%);
    transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    z-index: 100;
    box-shadow: 
      0 30px 60px rgba(0, 0, 0, 0.5),
      inset 0 1px 0 rgba(255, 255, 255, 0.1);
  }

  .sidebar.open {
    transform: translateY(0);
  }

  .card {
    padding: 24px;
    border-radius: 20px;
  }

  .question h2 {
    font-size: 20px;
  }

  .meta {
    gap: 12px;
  }

  .meta-item {
    padding: 6px 12px;
    font-size: 13px;
  }

  .actions {
    gap: 10px;
  }

  .btn {
    padding: 10px 16px;
    font-size: 13px;
  }
}

@media (max-width: 640px) {
  .app {
    padding: 0 16px 24px;
  }

  .topbar {
    flex-wrap: wrap;
    padding: 16px 0;
  }

  .topbar-left {
    flex: 1 1 100%;
    margin-bottom: 12px;
  }

  .meta {
    flex: 1 1 100%;
    justify-content: space-between;
  }

  .card {
    padding: 20px;
  }

  .question h2 {
    font-size: 18px;
  }

  .answer {
    padding: 16px 18px;
    font-size: 14px;
  }

  .actions {
    justify-content: stretch;
  }

  .btn {
    flex: 1;
    justify-content: center;
  }

  .sidebar {
    top: 120px;
    left: 16px;
    right: 16px;
  }
}