/* Font Size Tokens (TailwindCSS aligned) */
:root {
  /* Font Sizes */
  --font-xs: 12px;
  --font-sm: 14px;
  --font-base: 16px;
  --font-xl: 20px;
  --font-2xl: 24px;
  --font-3xl: 30px;

  /* Line Height Tokens */
  --line-height-normal: 1.6;
  --line-height-relaxed: 1.8;

  /* Spacing Tokens */
  --space-xs: 2px;
  --space-sm: 4px;
  --space-md: 8px;
  --space-lg: 12px;
  --space-xl: 16px;
  --space-2xl: 24px;

  /* Colors - Neutral (Tailwind Stone) */
  --color-neutral-50: #fafaf9;
  --color-neutral-100: #f5f5f4;
  --color-neutral-200: #e7e5e4;
  --color-neutral-300: #d6d3d1;
  --color-neutral-400: #a8a29e;
  --color-neutral-500: #78716c;
  --color-neutral-600: #57534e;
  --color-neutral-700: #44403c;
  --color-neutral-800: #292524;
  --color-neutral-900: #1c1917;

  /* Colors - Primary (Tailwind Orange) */
  --color-primary-50: #fff7ed;
  --color-primary-100: #ffedd5;
  --color-primary-200: #fed7aa;
  --color-primary-300: #fdba74;
  --color-primary-400: #fb923c;
  --color-primary-500: #f97316;
  --color-primary-600: #ea580c;
  --color-primary-700: #c2410c;

  /* Colors - Secondary (Tailwind Teal) */
  --color-secondary-50: #f0fdfa;
  --color-secondary-100: #ccfbf1;
  --color-secondary-200: #99f6e4;
  --color-secondary-300: #5eead4;
  --color-secondary-400: #2dd4bf;
  --color-secondary-500: #14b8a6;
  --color-secondary-600: #0d9488;
  --color-secondary-700: #0f766e;

  /* Colors - Success (Tailwind Green) */
  --color-success-50: #f0fdf4;
  --color-success-200: #bbf7d0;
  --color-success-500: #22c55e;
  --color-success-600: #16a34a;
  --color-success-700: #15803d;

  /* Colors - Error (Tailwind Red) */
  --color-error-50: #fef2f2;
  --color-error-500: #ef4444;
  --color-error-700: #b91c1c;

  /* Colors - Base */
  --color-white: #fff;
  --color-black: #000;

  /* Special colors */
  --color-border: var(--color-neutral-200);
  --color-border-light: var(--color-neutral-100);
  --color-bg-primary: var(--color-white);
  --color-bg-secondary: var(--color-neutral-50);
  --color-text-primary: var(--color-neutral-900);
  --color-text-secondary: var(--color-neutral-600);
  --color-text-muted: var(--color-neutral-400);
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
body {
  font-family: "Noto Sans TC", "Helvetica Neue", Arial, sans-serif;
  background: var(--color-neutral-100);
  color: var(--color-text-primary);
  min-height: 100vh;
}
#app {
  max-width: 780px;
  margin: 0 auto;
  padding: 1.5rem 1rem 4rem;
}
.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 0.75rem;
}
.logo {
  font-size: var(--font-xl);
  font-weight: 700;
  color: var(--color-text-primary);
}
.logo span {
  color: var(--color-primary-600);
}
.badge {
  font-size: var(--font-xs);
  background: var(--color-primary-50);
  color: var(--color-primary-600);
  padding: 4px 10px;
  border-radius: 20px;
  border: 1px solid var(--color-primary-200);
}
.progress-bar {
  height: 4px;
  background: var(--color-neutral-200);
  border-radius: 2px;
  overflow: hidden;
  margin-bottom: 1.25rem;
}
.progress-fill {
  height: 100%;
  background: var(--color-primary-500);
  border-radius: 2px;
  transition: width 0.4s;
}
.tabs {
  display: flex;
  border-bottom: 1px solid var(--color-border);
  margin-bottom: 1.5rem;
  overflow-x: auto;
  overflow-y: hidden;
  overscroll-behavior-x: contain;
  -webkit-overflow-scrolling: touch;
  gap: 0;
  scrollbar-width: none;
}
.tabs::-webkit-scrollbar {
  display: none;
}
.tab {
  padding: 10px 16px;
  font-size: var(--font-base);
  cursor: pointer;
  border: none;
  background: none;
  color: var(--color-text-secondary);
  border-bottom: 2px solid transparent;
  margin-bottom: -1px;
  transition: all 0.15s;
  white-space: nowrap;
  font-weight: 500;
  font-family: inherit;
  text-decoration: none;
}
.tab.active {
  color: var(--color-primary-600);
  border-bottom-color: var(--color-primary-500);
}
.tab:hover:not(.active) {
  color: var(--color-neutral-700);
}
.card {
  background: var(--color-bg-primary);
  border: 1px solid var(--color-border);
  border-radius: 12px;
  padding: 1.25rem;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.04);
}
.card + .card {
  margin-top: 1rem;
}
/* ── Grammar Card Component ── */
.gc {
  border-top: 3px solid var(--color-primary-400);
  padding: 1.5rem;
}
.gc-header {
  margin-bottom: 1rem;
}
.gc-grammar {
  display: block;
  font-size: 1.75rem;
  font-weight: 800;
  color: var(--color-text-primary);
  letter-spacing: -0.02em;
  line-height: 1.2;
}
.gc-reading {
  display: block;
  font-size: var(--font-sm);
  color: var(--color-text-muted);
  letter-spacing: 0.04em;
  margin-top: 0.3rem;
}
.gc-meaning {
  font-size: var(--font-xl);
  font-weight: 700;
  color: var(--color-text-primary);
  line-height: 1.3;
  margin-bottom: 0.625rem;
}
.gc-divider {
  border: none;
  border-top: 1px solid var(--color-border);
  margin: 1rem 0;
}
.gc-examples {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}
.gc-example {
  padding-left: 0.875rem;
  border-left: 2px solid var(--color-neutral-200);
}
.gc-jp {
  font-size: var(--font-sm);
  color: var(--color-text-primary);
  line-height: var(--line-height-relaxed);
}
.gc-zh {
  font-size: var(--font-sm);
  color: var(--color-text-muted);
  line-height: var(--line-height-relaxed);
  margin-top: 0.1rem;
}
.gc-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
  margin-top: 1rem;
  padding-top: 0.875rem;
  border-top: 1px solid var(--color-border-light);
}
.gc-supplement {
  width: 100%;
  font-size: var(--font-sm);
  color: var(--color-primary-600);
  line-height: var(--line-height-normal);
  white-space: pre-wrap;
}
.gc-page {
  font-size: var(--font-xs);
  color: var(--color-text-muted);
  margin-right: auto;
}
.section-label {
  font-size: var(--font-xs);
  text-transform: uppercase;
  color: var(--color-text-muted);
  margin-bottom: 0.5rem;
  letter-spacing: 0;
}
.reading {
  font-size: var(--font-sm);
  color: var(--color-text-muted);
  margin-bottom: 0.4rem;
}
.tags {
  display: flex;
  gap: 5px;
  flex-wrap: wrap;
  margin-top: 0.75rem;
}
.tag {
  font-size: var(--font-xs);
  padding: 3px 9px;
  border-radius: 12px;
  background: var(--color-primary-50);
  color: var(--color-primary-600);
  border: 1px solid var(--color-primary-100);
}
button {
  cursor: pointer;
  font-family: inherit;
}
.btn {
  padding: 8px 16px;
  border-radius: 8px;
  border: 1px solid var(--color-border);
  background: var(--color-bg-primary);
  font-size: var(--font-base);
  color: var(--color-text-secondary);
  transition: all 0.15s;
}
.btn:hover {
  background: var(--color-neutral-50);
  color: var(--color-text-primary);
  border-color: var(--color-neutral-300);
}
.btn-primary {
  background: var(--color-primary-600);
  color: var(--color-white);
  border-color: var(--color-primary-600);
}
.btn-primary:hover {
  background: var(--color-primary-700);
  color: var(--color-white);
  border-color: var(--color-primary-700);
}
.btn-secondary {
  background: var(--color-secondary-500);
  color: var(--color-white);
  border-color: var(--color-secondary-500);
  text-decoration: none;
}
.btn-secondary:hover {
  background: var(--color-secondary-600);
  color: var(--color-white);
  border-color: var(--color-secondary-600);
}
.btn-sm {
  padding: 5px 12px;
  font-size: var(--font-xs);
}
.btn-ghost {
  border-color: transparent;
  background: none;
  color: var(--color-primary-600);
  padding-left: 0;
}
.btn-ghost:hover {
  border-color: transparent;
  background: none;
  color: var(--color-primary-700);
}
.search-wrap {
  position: relative;
  margin-bottom: 0.75rem;
}
.search-box {
  width: 100%;
  padding: 10px 36px 10px 14px;
  border-radius: 8px;
  border: 1px solid var(--color-border);
  background: var(--color-bg-primary);
  color: var(--color-text-primary);
  font-size: var(--font-base);
  outline: none;
  font-family: inherit;
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.04);
}
.search-box:focus {
  border-color: var(--color-primary-400);
  box-shadow: 0 0 0 3px var(--color-primary-100);
}
.search-clear {
  position: absolute;
  right: 10px;
  top: 50%;
  transform: translateY(-50%);
  background: none;
  border: none;
  color: var(--color-neutral-400);
  font-size: var(--font-base);
  cursor: pointer;
  padding: 2px 6px;
}
.filter-row {
  display: flex;
  gap: 8px;
  align-items: center;
  margin-bottom: 1rem;
  flex-wrap: wrap;
}
.filter-count {
  font-size: var(--font-xs);
  color: var(--color-text-secondary);
}
.sort-tabs {
  display: flex;
  background: var(--color-neutral-200);
  border-radius: 9px;
  padding: 2px;
  gap: 2px;
}
.sort-tab {
  flex: 1;
  padding: 5px 10px;
  border: none;
  background: transparent;
  border-radius: 7px;
  font-size: var(--font-xs);
  color: var(--color-text-secondary);
  transition:
    background 0.15s,
    color 0.15s,
    box-shadow 0.15s;
  white-space: nowrap;
  font-family: inherit;
}
.sort-tab.active {
  background: var(--color-white);
  color: var(--color-text-primary);
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.12);
}
.grammar-list {
  display: flex;
  flex-direction: column;
}
.grammar-item {
  padding: 0.8rem 1rem;
  border-bottom: 1px solid var(--color-border-light);
  cursor: pointer;
  transition: background 0.1s;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
}
.grammar-item:last-child {
  border-bottom: none;
}
.grammar-item:hover {
  background: var(--color-primary-50);
}
.grammar-item-name {
  font-size: var(--font-base);
  font-weight: 700;
  color: var(--color-text-primary);
}
.grammar-item-meaning {
  font-size: var(--font-xs);
  color: var(--color-text-secondary);
  margin-top: 2px;
}
.cycle-badge {
  font-size: var(--font-xs);
  padding: 2px 7px;
  border-radius: 10px;
  background: linear-gradient(
    135deg,
    var(--color-success-50) 0%,
    var(--color-success-200) 100%
  );
  color: var(--color-success-600);
  border: 1px solid var(--color-success-200);
  white-space: nowrap;
  flex-shrink: 0;
}
/* question card */
.question-card {
  background: var(--color-bg-primary);
  border: 1px solid var(--color-border);
  border-radius: 12px;
  padding: 2rem;
  margin-bottom: 1rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.04);
}
.question-card .tags {
  justify-content: center;
}
.question-grammar {
  font-size: var(--font-3xl);
  font-weight: 700;
  color: var(--color-text-primary);
  margin: 1rem 0;
}
.question-options {
  width: 100%;
  margin-top: 1.5rem;
}
/* answer feedback */
.answer-feedback {
  margin-top: 1rem;
  text-align: left;
}
.answer-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.625rem 0.75rem;
  margin-bottom: 0.75rem;
}
.answer-bar .btn {
  flex-shrink: 0;
  margin-left: 1rem;
}
.answer-result-text {
  font-size: var(--font-base);
  font-weight: 700;
}
/* grid */
.grid2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  margin-bottom: 1rem;
}
@media (max-width: 500px) {
  .grid2 {
    grid-template-columns: 1fr;
  }
  .question-card {
    padding: 1rem 0.875rem;
  }
  .answer-option {
    padding: 8px 12px;
    margin-bottom: 6px;
  }
  .answer-bar {
    padding: 0.5rem 0;
  }
  .card {
    padding: 0.875rem;
  }
}
.select-input {
  padding: 8px 12px;
  border-radius: 8px;
  border: 1px solid var(--color-border);
  background: var(--color-bg-primary);
  color: var(--color-text-primary);
  font-size: var(--font-base);
  outline: none;
  font-family: inherit;
  max-width: 100%;
}
/* answer options */
.answer-option {
  display: block;
  width: 100%;
  padding: 12px 16px;
  border-radius: 8px;
  border: 1px solid var(--color-border);
  font-size: var(--font-base);
  color: var(--color-text-secondary);
  margin-bottom: 8px;
  transition: all 0.15s;
  text-align: left;
  background: var(--color-bg-primary);
  font-family: inherit;
}
.answer-option:hover:not(:disabled) {
  border-color: var(--color-primary-300);
  color: var(--color-text-primary);
  background: var(--color-primary-50);
}
.answer-option.correct {
  background: var(--color-success-50);
  border-color: var(--color-success-500);
  color: var(--color-success-700);
  font-weight: 600;
}
.answer-option.wrong {
  background: var(--color-error-50);
  border-color: var(--color-error-500);
  color: var(--color-error-700);
}
.answer-option.viewing {
  outline: 2px solid var(--color-neutral-700);
  outline-offset: 2px;
}
/* session */
.result-badge {
  font-size: var(--font-xs);
  padding: 2px 7px;
  border-radius: 10px;
  white-space: nowrap;
  flex-shrink: 0;
}
.result-badge.correct {
  background: var(--color-success-50);
  color: var(--color-success-600);
  border: 1px solid var(--color-success-200);
}
.result-badge.wrong {
  background: var(--color-error-50);
  color: var(--color-error-700);
  border: 1px solid var(--color-error-500);
}
.start-card {
  text-align: center;
  padding: 2.5rem 1.5rem;
}
.start-title {
  font-size: var(--font-xl);
  font-weight: 700;
  color: var(--color-text-primary);
  margin-bottom: 0.5rem;
}
.start-description {
  font-size: var(--font-base);
  color: var(--color-text-secondary);
  margin-bottom: 1.5rem;
  line-height: var(--line-height-relaxed);
}
.session-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
  font-size: var(--font-base);
  color: var(--color-text-secondary);
}
.question-prompt {
  color: var(--color-text-primary);
  line-height: var(--line-height-relaxed);
  margin: 0.75rem 0 1rem;
}
.question-prompt.jp {
  font-size: var(--font-xl);
  font-weight: 700;
}
/* pagination */
.pager {
  display: flex;
  gap: 6px;
  align-items: center;
  justify-content: center;
  margin-top: 1rem;
  flex-wrap: wrap;
}
.pager-btn {
  padding: 5px 10px;
  border-radius: 6px;
  border: 1px solid var(--color-border);
  background: var(--color-bg-primary);
  font-size: var(--font-xs);
  color: var(--color-text-secondary);
  cursor: pointer;
  font-family: inherit;
}
.pager-btn:hover {
  background: var(--color-neutral-50);
  border-color: var(--color-neutral-300);
}
.pager-btn.active {
  background: var(--color-primary-600);
  color: var(--color-white);
  border-color: var(--color-primary-600);
}
.pager-info {
  font-size: var(--font-xs);
  color: var(--color-text-secondary);
}