:root {
  --bg: #0f172a;
  --bg-card: #020617;
  --bg-soft: #020617;
  --accent: #38bdf8;
  --accent-soft: rgba(56, 189, 248, 0.15);
  --accent-strong: #0ea5e9;
  --text: #e5e7eb;
  --text-muted: #9ca3af;
  --danger: #f97373;
  --danger-soft: rgba(248, 113, 113, 0.18);
  --success: #34d399;
  --success-soft: rgba(52, 211, 153, 0.16);
  --border-soft: rgba(148, 163, 184, 0.2);
  --radius-lg: 18px;
  --radius-full: 999px;
  --shadow-lg: 0 18px 50px rgba(15, 23, 42, 0.85);
  --shadow-soft: 0 4px 20px rgba(15, 23, 42, 0.6);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "SF Pro Text",
    "Segoe UI", sans-serif;
  background: radial-gradient(circle at top, #1f2937 0, #020617 45%, #020617 100%);
  color: var(--text);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: stretch;
  padding: 24px;
}

.app-shell {
  width: 100%;
  max-width: 980px;
  margin: auto;
  background:
    radial-gradient(circle at top left, rgba(56, 189, 248, 0.04) 0, transparent 60%),
    radial-gradient(circle at bottom right, rgba(52, 211, 153, 0.04) 0, transparent 60%),
    linear-gradient(135deg, rgba(15, 23, 42, 0.98), rgba(15, 23, 42, 0.98));
  border-radius: 26px;
  padding: 18px 16px 16px;
  box-shadow: var(--shadow-lg);
  border: 1px solid rgba(148, 163, 184, 0.30);
  display: flex;
  flex-direction: column;
  gap: 14px;
}

@media (min-width: 900px) {
  .app-shell {
    padding: 20px 22px 22px;
    gap: 16px;
  }
}

.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.app-title {
  display: flex;
  align-items: center;
  gap: 10px;
}

.app-logo {
  width: 32px;
  height: 32px;
  border-radius: 12px;
  background: radial-gradient(circle at 30% 30%, #38bdf8 0, #0f172a 40%, #020617 100%);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 18px;
  color: #e5f6ff;
  box-shadow: var(--shadow-soft);
}

.app-heading h1 {
  margin: 0;
  font-size: 19px;
  letter-spacing: 0.02em;
  font-weight: 600;
}

.app-heading span {
  margin: 0;
  font-size: 11px;
  color: var(--text-muted);
}

.controls {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.file-input-label {
  position: relative;
  overflow: hidden;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 10px;
  font-size: 11px;
  border-radius: var(--radius-full);
  border: 1px dashed rgba(148, 163, 184, 0.6);
  color: var(--text);
  cursor: pointer;
  background: rgba(15, 23, 42, 0.85);
  backdrop-filter: blur(14px);
}

.file-input-label input[type="file"] {
  position: absolute;
  inset: 0;
  opacity: 0;
  cursor: pointer;
}

.pill-btn {
  border-radius: var(--radius-full);
  padding: 6px 12px;
  font-size: 11px;
  border: 1px solid rgba(148, 163, 184, 0.6);
  background: rgba(15, 23, 42, 0.9);
  color: var(--text);
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 4px;
}

.session-timer-pill {
  padding: 8px 14px;
  font-size: 13px;
  border-radius: var(--radius-full);
  background: rgba(14, 165, 233, 0.15);
  /* light blue semi-transparent */
  color: var(--accent-strong);
  font-weight: 600;
  border: 1px solid rgba(14, 165, 233, 0.3);
  display: inline-flex;
  align-items: center;
  margin-left: 8px;
  /* space between decks button */
  margin-top: 10px;
  /* added vertical padding above the pill as requested */
}

.pill-btn.primary {
  background: radial-gradient(circle at top left, var(--accent-strong), var(--accent));
  border-color: transparent;
  color: #0b1220;
  font-weight: 500;
}

.pill-btn.danger-soft {
  border-color: rgba(248, 113, 113, 0.5);
  color: #fecaca;
}

.pill-btn:disabled {
  cursor: default;
  opacity: 0.4;
}

.pill-btn:hover:not(:disabled) {
  filter: brightness(1.05);
}

.body-layout {
  display: grid;
  grid-template-columns: minmax(0, 3fr) minmax(0, 1.4fr);
  gap: 14px;
}

@media (max-width: 900px) {
  body {
    padding: 12px;
  }

  .app-shell {
    border-radius: 18px;
    padding: 14px 12px 12px;
  }

  .body-layout {
    grid-template-columns: 1fr;
  }

  .app-header {
    flex-direction: column;
    align-items: stretch;
  }

  .controls {
    justify-content: space-between;
    margin-top: 8px;
  }

  .pill-btn {
    padding: 8px 14px;
    font-size: 13px;
  }

  .file-input-label {
    padding: 8px 14px;
    font-size: 13px;
  }
}

.options {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.tag {
  font-size: 11px;
  padding: 2px 8px;
  border-radius: var(--radius-full);
  border: 1px solid rgba(148, 163, 184, 0.4);
  color: var(--text-muted);
  background: rgba(15, 23, 42, 0.9);
}

/* Drag and Drop Welcome Screen Styles */
.welcome-screen {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-card);
  border-radius: 20px;
  z-index: 10;
  padding: 20px;
}

.welcome-box {
  text-align: center;
  padding: 40px 20px;
  border: 2px dashed rgba(148, 163, 184, 0.4);
  border-radius: 20px;
  background: rgba(15, 23, 42, 0.4);
  transition: all 0.2s ease;
  width: 100%;
  max-width: 400px;
}

.welcome-box.drag-over {
  border-color: var(--accent-strong);
  background: rgba(56, 189, 248, 0.1);
  transform: scale(1.02);
}

.welcome-icon {
  font-size: 48px;
  margin-bottom: 16px;
  animation: float 3s ease-in-out infinite;
}

@keyframes float {

  0%,
  100% {
    transform: translateY(0);
  }

  50% {
    transform: translateY(-10px);
  }
}

.welcome-box h2 {
  font-size: 20px;
  font-weight: 600;
  margin: 0 0 12px 0;
  color: var(--text);
}

.welcome-box p {
  color: var(--text-muted);
  font-size: 14px;
  margin: 0 0 16px 0;
}

.welcome-box .welcome-hint {
  font-size: 12px;
  color: var(--accent-strong);
}

.card {
  position: relative;
  /* important for absolute positioning of welcome screen */
  background: radial-gradient(circle at top, rgba(15, 23, 42, 0.9) 0, rgba(15, 23, 42, 0.98) 50%);
  border-radius: 20px;
  padding: 16px 16px 14px;
  border: 1px solid rgba(148, 163, 184, 0.5);
  box-shadow: var(--shadow-soft);
  display: flex;
  flex-direction: column;
  gap: 12px;
  overflow: hidden;
  /* Ensure welcome screen doesn't overflow */
}

@media (min-width: 900px) {
  .card {
    padding: 18px;
  }
}

.card-header {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.session-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 8px;
  font-size: 11px;
  color: var(--text-muted);
}

.session-tags {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
  align-items: center;
}

.session-timer {
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas;
  font-size: 11px;
  padding: 3px 8px;
  border-radius: var(--radius-full);
  border: 1px solid rgba(148, 163, 184, 0.5);
  background: rgba(15, 23, 42, 0.9);
  color: var(--accent-strong);
}

.question-meta {
  display: flex;
  align-items: baseline;
  gap: 10px;
  flex-wrap: wrap;
}

.question-label {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--accent-strong);
}

.question-id {
  font-size: 11px;
  color: var(--text-muted);
}

.question-stats-inline {
  margin-left: auto;
  font-size: 11px;
  color: var(--text-muted);
}

.question-text {
  font-size: 14px;
  line-height: 1.5;
  padding: 10px 11px;
  border-radius: 14px;
  background:
    radial-gradient(circle at top left, rgba(56, 189, 248, 0.08) 0, transparent 55%),
    radial-gradient(circle at bottom right, rgba(52, 211, 153, 0.06) 0, transparent 50%),
    #020617;
  border: 1px solid rgba(148, 163, 184, 0.45);
}

.option-btn {
  border-radius: 14px;
  padding: 12px 14px;
  /* increased padding for mobile touch targets */
  border: 1px solid rgba(148, 163, 184, 0.45);
  background: radial-gradient(circle at top left, rgba(15, 23, 42, 0.95) 0, #020617 50%);
  color: var(--text);
  font-size: 14px;
  /* slightly larger text */
  text-align: left;
  cursor: pointer;
  display: flex;
  align-items: flex-start;
  gap: 10px;
  transition: transform 0.05s ease, box-shadow 0.05s ease, border-color 0.08s ease,
    background 0.08s ease;
  min-height: 48px;
  /* accessibility standard */
}

.option-btn span.letter {
  font-size: 11px;
  font-weight: 600;
  padding: 3px 7px;
  border-radius: var(--radius-full);
  border: 1px solid rgba(148, 163, 184, 0.5);
  color: var(--text-muted);
  flex-shrink: 0;
}

.option-btn span.text {
  flex: 1;
}

.option-btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 8px 26px rgba(15, 23, 42, 0.7);
  border-color: rgba(56, 189, 248, 0.6);
  background: radial-gradient(circle at top left, rgba(56, 189, 248, 0.18) 0, #020617 55%);
}

.option-btn:disabled {
  cursor: default;
  transform: none;
  box-shadow: none;
}

.option-btn.correct {
  border-color: var(--success);
  background: var(--success-soft);
}

.option-btn.incorrect {
  border-color: var(--danger);
  background: var(--danger-soft);
}

.option-btn.selected:not(.correct):not(.incorrect) {
  border-color: rgba(56, 189, 248, 0.85);
  background: var(--accent-soft);
}

.feedback-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  font-size: 11px;
  color: var(--text-muted);
}

.feedback-pill {
  padding: 3px 9px;
  border-radius: var(--radius-full);
  font-size: 11px;
  display: inline-flex;
  align-items: center;
  gap: 5px;
}

.feedback-pill.success {
  background: var(--success-soft);
  color: var(--success);
}

.feedback-pill.error {
  background: var(--danger-soft);
  color: #fecaca;
}

.feedback-pill.neutral {
  background: rgba(148, 163, 184, 0.18);
  color: var(--text-muted);
}

.feedback-pill span.icon {
  font-size: 12px;
}

.explanation {
  margin-top: 6px;
  padding: 8px 10px;
  border-radius: 14px;
  border: 1px dashed rgba(148, 163, 184, 0.4);
  background:
    radial-gradient(circle at top right, rgba(56, 189, 248, 0.10) 0, rgba(15, 23, 42, 0.96) 55%);
  font-size: 12px;
  line-height: 1.5;
  display: none;
}

.explanation.visible {
  display: block;
}

.explanation-title {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--accent-strong);
  margin-bottom: 4px;
}

.card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  margin-top: 2px;
}

.footer-left {
  display: flex;
  gap: 6px;
  align-items: center;
  flex-wrap: wrap;
  font-size: 11px;
  color: var(--text-muted);
}

.footer-right {
  display: flex;
  gap: 6px;
  align-items: center;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.secondary-btn {
  background: transparent;
  border-radius: var(--radius-full);
  border: 1px solid rgba(148, 163, 184, 0.55);
  color: var(--text-muted);
  font-size: 12px;
  padding: 6px 12px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 4px;
  min-height: 36px;
}

.secondary-btn:disabled {
  opacity: 0.4;
  cursor: default;
}

/* Custom Modal Styles */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(2, 6, 23, 0.8);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 9999;
}

.modal-box {
  background: var(--bg-card);
  border: 1px solid rgba(148, 163, 184, 0.2);
  border-radius: 20px;
  padding: 24px;
  max-width: 400px;
  width: 90%;
  box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
  text-align: center;
  animation: modalPop 0.2s ease-out;
}

@keyframes modalPop {
  0% {
    transform: scale(0.95);
    opacity: 0;
  }

  100% {
    transform: scale(1);
    opacity: 1;
  }
}

.modal-box h3 {
  margin: 0 0 12px 0;
  font-size: 18px;
  color: var(--text);
}

.modal-box .modal-message {
  margin: 0 0 24px 0;
  font-size: 14px;
  color: var(--text-muted);
  line-height: 1.5;
  text-align: left;
}

.modal-table {
  width: 100%;
  border-collapse: collapse;
  margin: 16px 0;
  font-size: 13px;
  text-align: left;
}

.modal-table th,
.modal-table td {
  padding: 8px 12px;
  border-bottom: 1px solid rgba(148, 163, 184, 0.2);
}

.modal-table th {
  font-weight: 600;
  color: var(--text);
  background: rgba(15, 23, 42, 0.4);
}

.modal-summary-row {
  display: flex;
  justify-content: space-between;
  padding: 8px 0;
  border-bottom: 1px solid rgba(148, 163, 184, 0.1);
}

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

.modal-summary-row .label {
  font-weight: 500;
  color: var(--text);
}

.modal-summary-row .value {
  color: var(--accent-strong);
  font-weight: 600;
}

.modal-message strong {
  color: var(--text);
}

.modal-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
}

.secondary-btn:hover:not(:disabled) {
  border-color: rgba(148, 163, 184, 0.9);
}

.side-card {
  background: radial-gradient(circle at top, rgba(15, 23, 42, 0.9) 0, rgba(15, 23, 42, 1) 52%);
  border-radius: 18px;
  padding: 10px 10px 10px;
  border: 1px solid rgba(148, 163, 184, 0.45);
  box-shadow: var(--shadow-soft);
  font-size: 11px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.side-title {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 8px;
  font-size: 12px;
}

.side-title span.muted {
  color: var(--text-muted);
  font-size: 11px;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 6px;
}

.stat-chip {
  background: rgba(15, 23, 42, 0.98);
  border-radius: 12px;
  padding: 7px 8px;
  border: 1px solid rgba(148, 163, 184, 0.5);
  display: flex;
  flex-direction: column;
  gap: 2px;
  min-height: 44px;
}

.stat-label {
  font-size: 10px;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.09em;
}

.stat-value {
  font-size: 14px;
  font-weight: 600;
}

.stat-sub {
  font-size: 10px;
  color: var(--text-muted);
}

.filters-row {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}

.filter-pill {
  border-radius: var(--radius-full);
  padding: 3px 9px;
  border: 1px solid rgba(148, 163, 184, 0.55);
  font-size: 10px;
  color: var(--text-muted);
  cursor: pointer;
  background: rgba(15, 23, 42, 0.95);
}

.filter-pill.active {
  border-color: var(--accent-strong);
  background: var(--accent-soft);
  color: var(--accent-strong);
}

.hint-text {
  font-size: 10px;
  color: var(--text-muted);
  opacity: 0.9;
}

.divider {
  height: 1px;
  background: linear-gradient(to right, transparent, rgba(148, 163, 184, 0.45), transparent);
  margin: 2px 0 4px;
}

.empty-state {
  font-size: 12px;
  color: var(--text-muted);
  text-align: center;
  padding: 8px 8px 4px;
}

.empty-state strong {
  color: var(--accent);
}

.active-bookmark {
  border-color: rgba(250, 204, 21, 0.9) !important;
}

.tabs-header {
  display: flex;
  gap: 6px;
  border-bottom: 1px solid rgba(148, 163, 184, 0.35);
  padding-bottom: 4px;
  margin-bottom: 6px;
}

.tab-btn {
  flex: 1;
  padding: 5px 6px;
  font-size: 11px;
  border-radius: 999px;
  border: 1px solid transparent;
  background: transparent;
  color: var(--text-muted);
  cursor: pointer;
  text-align: center;
  white-space: nowrap;
}

.tab-btn.active {
  border-color: rgba(148, 163, 184, 0.7);
  background: rgba(15, 23, 42, 0.9);
  color: var(--accent-strong);
}

.tab-panel {
  display: none;
  flex-direction: column;
  gap: 6px;
}

.tab-panel.active {
  display: flex;
}

.deck-select {
  border-radius: var(--radius-full);
  border: 1px solid rgba(148, 163, 184, 0.55);
  background: rgba(15, 23, 42, 0.95);
  color: var(--text);
  font-size: 11px;
  padding: 3px 8px;
}

.deck-panel {
  margin-top: 6px;
  padding: 8px 10px;
  border-radius: 14px;
  border: 1px solid rgba(148, 163, 184, 0.5);
  background: rgba(15, 23, 42, 0.98);
  font-size: 11px;
}

.deck-panel-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  margin-bottom: 4px;
}

.deck-checkbox-list {
  display: flex;
  flex-direction: column;
  gap: 2px;
  max-height: 120px;
  overflow: auto;
  margin-bottom: 4px;
}

.deck-checkbox-list label {
  display: flex;
  align-items: center;
  gap: 4px;
}

.deck-checkbox-list input[type="checkbox"] {
  flex-shrink: 0;
}

.deck-summary-list {
  display: flex;
  flex-direction: column;
  gap: 4px;
  font-size: 11px;
}

.deck-summary-item {
  border-radius: 10px;
  border: 1px solid rgba(148, 163, 184, 0.4);
  padding: 6px 8px;
  background: rgba(15, 23, 42, 0.96);
}

.deck-summary-title {
  font-weight: 500;
  font-size: 11px;
}

.deck-summary-meta {
  font-size: 10px;
  color: var(--text-muted);
}