:root {
  color-scheme: light;
  font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, sans-serif;
  line-height: 1.4;
  background: #f6f7f9;
  color: #16181d;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
}

button,
select {
  touch-action: manipulation;
}

.layout {
  max-width: 920px;
  margin: 0 auto;
  padding: 24px 16px 110px;
}

.header h1 {
  margin: 0 0 6px;
  font-size: 1.5rem;
}

.header p {
  margin: 0;
  color: #4f5565;
}

.controls {
  margin-top: 10px;
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
}

.controls label {
  font-size: 0.85rem;
  color: #4f5565;
}

.controls select {
  min-width: 0;
  width: min(100%, 420px);
  border: 1px solid #d3dbe7;
  border-radius: 8px;
  background: #fff;
  padding: 6px 10px;
  font-size: 0.9rem;
  color: #1d2432;
}

.tag-controls {
  margin-top: 10px;
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 0.85rem;
  color: #4f5565;
}

.tag-controls button {
  border: 1px solid #d3dbe7;
  border-radius: 999px;
  padding: 4px 10px;
  background: #fff;
  color: #364154;
  cursor: pointer;
}

.tag-controls button.active {
  border-color: #2f7d48;
  background: #eaf8ef;
  color: #1d5e34;
}

.tag-controls button:disabled {
  opacity: 0.5;
  cursor: default;
}

.floating-nav {
  position: fixed;
  left: 50%;
  bottom: 16px;
  transform: translateX(-50%);
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 10px;
  border: 1px solid #cad5e6;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.94);
  backdrop-filter: blur(8px);
  box-shadow: 0 8px 22px rgba(29, 38, 56, 0.14);
  z-index: 40;
}

.floating-nav button {
  border: 1px solid #c5d0e3;
  border-radius: 999px;
  background: #fff;
  color: #31405b;
  font-size: 0.82rem;
  padding: 5px 11px;
  cursor: pointer;
}

.floating-nav button:hover {
  background: #f7faff;
}

.tag-filter-list {
  margin-top: 8px;
  display: flex;
  flex-wrap: wrap;
  gap: 7px;
}

.tag-filter-empty {
  color: #6a778f;
  font-size: 0.85rem;
}

.tag-filter {
  border: 1px solid #d1d8e6;
  border-radius: 999px;
  background: #fff;
  color: #3a465d;
  padding: 4px 10px;
  font-size: 0.8rem;
  cursor: pointer;
}

.tag-filter.active {
  border-color: #2f7d48;
  background: #eaf8ef;
  color: #1d5e34;
}

.error {
  margin-top: 16px;
  background: #ffe7e7;
  border: 1px solid #ffb9b9;
  color: #8f1010;
  border-radius: 8px;
  padding: 10px 12px;
}

.hidden {
  display: none;
}

.questions {
  display: grid;
  gap: 14px;
  margin-top: 20px;
}

.quiz-section {
  scroll-margin-top: 12px;
}

.quiz-section-header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 10px;
  margin: 2px 2px 10px;
}

.quiz-section-title {
  margin: 0;
  font-size: 1rem;
  color: #202839;
}

.quiz-section-count {
  font-size: 0.8rem;
  color: #5e6b83;
  white-space: nowrap;
}

.quiz-section-cards {
  display: grid;
  gap: 14px;
}

.card {
  background: #fff;
  border: 1px solid #dde2ea;
  border-radius: 10px;
  padding: clamp(11px, 1.8vw, 14px);
  width: 100%;
  max-width: 100%;
  overflow-wrap: break-word;
}

@supports (content-visibility: auto) {
  .card {
    content-visibility: auto;
    contain-intrinsic-size: auto 900px;
  }
}

.card-favorited {
  border-color: #f0cb64;
  box-shadow: inset 0 0 0 1px #f8e3a2;
}

.card-top {
  display: flex;
  justify-content: space-between;
  gap: 8px;
  align-items: flex-start;
}

.card h2 {
  margin: 0 0 4px;
  font-size: clamp(0.98rem, 2.8vw, 1.1rem);
  min-width: 0;
  overflow-wrap: anywhere;
}

.card-actions {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.action-btn {
  border: 1px solid #c9d4e7;
  background: #fff;
  color: #30415b;
  border-radius: 999px;
  padding: clamp(5px, 1.2vw, 7px) clamp(9px, 2.1vw, 12px);
  font-size: clamp(0.74rem, 2.1vw, 0.78rem);
  cursor: pointer;
  white-space: nowrap;
}

.action-btn:disabled {
  opacity: 0.6;
  cursor: default;
}

.favorite-btn.active {
  border-color: #d9ab2a;
  background: #fff7e1;
  color: #7b5600;
}

.meta {
  margin-bottom: 10px;
  font-size: 0.9rem;
  color: #555f74;
}

.question-tags {
  margin-bottom: 10px;
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.tag-chip {
  border: 1px solid #cfd8e8;
  border-radius: 999px;
  padding: 2px 8px;
  font-size: 0.75rem;
  color: #3d4c68;
  background: #f8fbff;
}

.choices {
  margin: 10px 0;
  padding-left: 0;
  list-style: none;
  display: grid;
  gap: 8px;
}

.choice {
  border: 1px solid #e2e6ee;
  border-radius: 8px;
  padding: clamp(7px, 1.6vw, 10px);
  background: #fbfcfe;
}

.choice-correct {
  border-color: #8cce9e;
  background: #eefcf0;
}

.choice-line {
  display: flex;
  align-items: flex-start;
  gap: 8px;
  min-width: 0;
  flex-wrap: wrap;
}

.choice-index {
  font-weight: 600;
  min-width: 20px;
}

.choice-text {
  flex: 1;
  min-width: 0;
  overflow-wrap: anywhere;
}

.markdown {
  min-width: 0;
  overflow-wrap: anywhere;
}

.choice-text > :first-child {
  margin-top: 0;
}

.choice-text > :last-child {
  margin-bottom: 0;
}

.badge {
  font-size: clamp(0.7rem, 1.9vw, 0.75rem);
  background: #2b7a3b;
  color: #fff;
  padding: 2px 8px;
  border-radius: 999px;
}

.explanation-toggle {
  margin-top: 12px;
  border: 1px solid #d7deeb;
  border-radius: 8px;
  background: #f8fafc;
  padding: 10px;
}

.explanation-toggle summary {
  cursor: pointer;
  color: #33415a;
  font-weight: 600;
  font-size: 0.84rem;
  list-style: none;
}

.explanation-toggle summary::-webkit-details-marker {
  display: none;
}

.explanation-content {
  margin-top: 8px;
}

.explanation-content.empty {
  color: #616d84;
  font-size: 0.85rem;
}

.markdown img {
  max-width: 100%;
  height: auto;
  display: block;
}

.markdown > :first-child {
  margin-top: 0;
}

.markdown > :last-child {
  margin-bottom: 0;
}

.markdown-small {
  font-size: clamp(0.84rem, 2.3vw, 0.88rem);
  line-height: 1.35;
}

@media (max-width: 560px) {
  .card {
    content-visibility: visible;
    contain-intrinsic-size: none;
  }

  .card {
    border-radius: 9px;
  }

  .card-top {
    gap: 6px;
  }

  .card-actions {
    gap: 5px;
  }

  .meta {
    font-size: 0.84rem;
  }

  .quiz-section-title {
    font-size: 0.92rem;
  }

  .quiz-section-count {
    font-size: 0.74rem;
  }

  .tag-chip {
    font-size: 0.72rem;
  }
}

@media (max-width: 640px) {
  .layout {
    padding-bottom: 134px;
  }

  .header h1 {
    font-size: 1.3rem;
  }

  .header p {
    font-size: 0.88rem;
  }

  .controls {
    gap: 10px;
    align-items: stretch;
  }

  .controls label {
    width: 100%;
    font-size: 0.84rem;
  }

  .controls select {
    font-size: 0.88rem;
    min-height: 44px;
    padding: 9px 12px;
  }

  .tag-controls {
    font-size: 0.8rem;
    gap: 8px;
  }

  .tag-controls button,
  .tag-filter {
    font-size: 0.8rem;
    min-height: 40px;
    padding: 8px 12px;
  }

  .action-btn {
    min-height: 38px;
  }

  .card {
    font-size: 0.94rem;
  }

  .card h2 {
    font-size: 0.95rem;
  }

  .action-btn {
    font-size: 0.72rem;
  }

  .choice-index {
    min-width: 18px;
    font-size: 0.95rem;
  }

  .badge {
    font-size: 0.66rem;
  }

  .explanation-toggle summary {
    font-size: 0.8rem;
  }

  .markdown-small {
    font-size: 0.8rem;
  }

  .floating-nav {
    left: 0;
    right: 0;
    bottom: 0;
    transform: none;
    width: 100%;
    justify-content: center;
    gap: 10px;
    padding: 8px 12px calc(8px + env(safe-area-inset-bottom));
    border-radius: 0;
    border-left: none;
    border-right: none;
    border-bottom: none;
    box-shadow: 0 -8px 22px rgba(29, 38, 56, 0.16);
    backdrop-filter: blur(6px);
  }

  .floating-nav button {
    flex: 1;
    text-align: center;
    font-size: 0.82rem;
    min-height: 44px;
    padding: 9px 10px;
  }
}

@media (max-width: 420px) {
  .header h1 {
    font-size: 1.2rem;
  }

  .card {
    font-size: 0.9rem;
  }

  .card h2 {
    font-size: 0.9rem;
  }

  .meta {
    font-size: 0.78rem;
  }

  .action-btn {
    font-size: 0.7rem;
    min-height: 36px;
  }

  .tag-controls button,
  .tag-filter {
    font-size: 0.76rem;
    min-height: 38px;
    padding: 7px 11px;
  }

  .floating-nav {
    gap: 8px;
    padding: 8px 8px calc(8px + env(safe-area-inset-bottom));
  }

  .floating-nav button {
    font-size: 0.78rem;
    min-height: 42px;
    padding: 8px 9px;
  }
}