:root {
  --bg: #0f0f12;
  --bg-card: #16181f;
  --bg-elevated: #1c1f28;
  --border: #2a2e3a;
  --text: #e8eaed;
  --text-muted: #9aa0a6;
  --silver: #c0c0c0;
  --silver-dim: #8a8f98;
  --accent: #00d4ff;
  --accent-hover: #00b8e0;
  --success: #34d399;
  --warning: #fbbf24;
  --danger: #f87171;
  --radius: 12px;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.4);
  --font: 'Inter', system-ui, -apple-system, sans-serif;
  --mono: 'JetBrains Mono', ui-monospace, monospace;
}

[data-theme="light"] {
  --bg: #f4f5f7;
  --bg-card: #ffffff;
  --bg-elevated: #f0f1f3;
  --border: #e0e3e8;
  --text: #1a1d24;
  --text-muted: #5f6368;
  --silver: #5a5e66;
  --shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

.container {
  width: 100%;
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 1.25rem;
}

/* Header */
.header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(15, 15, 18, 0.85);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  padding: 0.75rem 0;
}

[data-theme="light"] .header {
  background: rgba(244, 245, 247, 0.9);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.logo-icon {
  width: 40px;
  height: 40px;
}

.logo h1 {
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.logo h1 span {
  color: var(--accent);
  font-weight: 600;
}

.tagline {
  font-size: 0.75rem;
  color: var(--text-muted);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.user-info {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.avatar {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  object-fit: cover;
  border: 2px solid var(--border);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  padding: 0.55rem 1.1rem;
  font-size: 0.9rem;
  font-weight: 500;
  font-family: inherit;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.2s ease;
  white-space: nowrap;
}

.btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent), #0099cc);
  color: #0a0a0c;
  font-weight: 600;
}

.btn-primary:hover:not(:disabled) {
  background: linear-gradient(135deg, var(--accent-hover), #0088b8);
  transform: translateY(-1px);
  box-shadow: 0 4px 16px rgba(0, 212, 255, 0.3);
}

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

.btn-secondary:hover:not(:disabled) {
  border-color: var(--accent);
  color: var(--accent);
}

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

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

.btn-sm {
  padding: 0.35rem 0.75rem;
  font-size: 0.8rem;
}

.btn-lg {
  padding: 0.85rem 1.75rem;
  font-size: 1.05rem;
}

.btn-icon {
  background: transparent;
  border: none;
  font-size: 1.2rem;
  cursor: pointer;
  padding: 0.4rem;
  border-radius: 8px;
}

.btn-icon:hover {
  background: var(--bg-elevated);
}

.btn-group {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
}

/* Cards */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
  box-shadow: var(--shadow);
}

.card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1rem;
  gap: 0.75rem;
}

.card-header h2 {
  font-size: 1.1rem;
  font-weight: 600;
}

.badge {
  font-size: 0.75rem;
  padding: 0.2rem 0.55rem;
  background: var(--bg-elevated);
  border-radius: 999px;
  color: var(--text-muted);
  font-family: var(--mono);
}

/* Main layout */
.main {
  padding: 1.5rem 1.25rem 3rem;
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.grid-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.25rem;
}

@media (max-width: 768px) {
  .grid-2 {
    grid-template-columns: 1fr;
  }
}

/* Upload zone */
.upload-zone {
  border: 2px dashed var(--border);
  border-radius: 10px;
  padding: 1.75rem 1rem;
  text-align: center;
  cursor: pointer;
  transition: all 0.2s ease;
  background: var(--bg-elevated);
}

.upload-zone:hover,
.upload-zone.dragover {
  border-color: var(--accent);
  background: rgba(0, 212, 255, 0.06);
}

.upload-icon {
  font-size: 2rem;
  margin-bottom: 0.5rem;
}

.upload-zone p {
  font-size: 0.9rem;
  color: var(--text);
}

.hint {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: 0.25rem;
}

.file-list {
  margin-top: 0.75rem;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  max-height: 160px;
  overflow-y: auto;
}

.file-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.4rem 0.6rem;
  background: var(--bg-elevated);
  border-radius: 6px;
  font-size: 0.85rem;
}

.file-item .name {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  max-width: 70%;
}

.file-item .remove {
  color: var(--danger);
  cursor: pointer;
  font-size: 1rem;
  background: none;
  border: none;
}

.checkbox-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-top: 0.85rem;
  font-size: 0.9rem;
  cursor: pointer;
}

.checkbox-row input {
  accent-color: var(--accent);
  width: 1.1rem;
  height: 1.1rem;
}

/* Form */
.form-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.form-group label {
  font-size: 0.8rem;
  color: var(--text-muted);
  font-weight: 500;
}

.form-group input {
  padding: 0.55rem 0.75rem;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  font-family: inherit;
  font-size: 0.9rem;
}

.form-group input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(0, 212, 255, 0.15);
}

/* Action bar */
.action-bar {
  text-align: center;
  padding: 0.5rem 0 1rem;
}

/* Progress */
.progress-card {
  border-color: var(--accent);
}

.progress-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.75rem;
}

.progress-bar-wrap {
  height: 8px;
  background: var(--bg-elevated);
  border-radius: 999px;
  overflow: hidden;
  margin-bottom: 0.6rem;
}

.progress-bar {
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, var(--accent), #34d399);
  border-radius: 999px;
  transition: width 0.35s ease;
}

.progress-status {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.mono {
  font-family: var(--mono);
  font-size: 0.9rem;
}

/* Results */
.results-list {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.result-item {
  border: 1px solid var(--border);
  border-radius: 10px;
  overflow: hidden;
}

.result-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.85rem 1rem;
  cursor: pointer;
  background: var(--bg-elevated);
  transition: background 0.15s;
}

.result-header:hover {
  background: rgba(0, 212, 255, 0.08);
}

.result-name {
  font-weight: 600;
}

.result-score {
  font-family: var(--mono);
  font-weight: 600;
  color: var(--accent);
}

.result-body {
  display: none;
  padding: 1rem;
  border-top: 1px solid var(--border);
  background: var(--bg-card);
}

.result-item.open .result-body {
  display: block;
}

.qa-row {
  display: grid;
  grid-template-columns: 40px 1fr 1fr;
  gap: 0.5rem;
  padding: 0.4rem 0;
  border-bottom: 1px solid var(--border);
  font-size: 0.85rem;
}

.qa-row:last-child {
  border-bottom: none;
}

.qa-num {
  font-family: var(--mono);
  color: var(--text-muted);
}

.qa-correct {
  color: var(--success);
}

.qa-wrong {
  color: var(--danger);
}

/* Modal */
.modal {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.7);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 100;
  padding: 1rem;
}

.modal.hidden {
  display: none;
}

.modal-content {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  max-width: 420px;
  width: 100%;
  box-shadow: var(--shadow);
}

.modal-content h2 {
  margin-bottom: 0.5rem;
}

.modal-content p {
  font-size: 0.9rem;
  color: var(--text-muted);
  margin-bottom: 1rem;
}

.modal-content .form-group {
  margin-bottom: 0.85rem;
}

.modal-content .btn-group {
  margin-top: 1.25rem;
}

/* Footer */
.footer {
  border-top: 1px solid var(--border);
  padding: 1.5rem 0;
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-muted);
}

.footer a {
  color: var(--accent);
  text-decoration: none;
}

.footer .small {
  font-size: 0.75rem;
  margin-top: 0.35rem;
}

/* Utils */
.hidden {
  display: none !important;
}

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

::-webkit-scrollbar-track {
  background: var(--bg);
}

::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 3px;
}