/* ===== Reset & Base ===== */
* { box-sizing: border-box; margin: 0; padding: 0; }
html, body { height: 100%; }

:root {
  --color-bg: #f4f6f9;
  --color-card: #ffffff;
  --color-text: #1f2937;
  --color-muted: #6b7280;
  --color-primary: #1e6091;
  --color-primary-dark: #144b73;
  --color-success: #15803d;
  --color-success-bg: #dcfce7;
  --color-danger: #b91c1c;
  --color-danger-bg: #fee2e2;
  --color-border: #e5e7eb;
  --color-tag-bg: #eff6ff;
  --color-tag-text: #1e6091;
  --radius: 12px;
  --shadow: 0 2px 8px rgba(0,0,0,0.08);
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #0f172a;
    --color-card: #1e293b;
    --color-text: #e2e8f0;
    --color-muted: #94a3b8;
    --color-primary: #3b82f6;
    --color-primary-dark: #2563eb;
    --color-success: #4ade80;
    --color-success-bg: #14532d;
    --color-danger: #f87171;
    --color-danger-bg: #7f1d1d;
    --color-border: #334155;
    --color-tag-bg: #1e3a5f;
    --color-tag-text: #93c5fd;
    --shadow: 0 2px 12px rgba(0,0,0,0.4);
  }
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Hiragino Sans",
    "Hiragino Kaku Gothic ProN", "Yu Gothic UI", "Yu Gothic", Meiryo, sans-serif;
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  padding: env(safe-area-inset-top) env(safe-area-inset-right)
           env(safe-area-inset-bottom) env(safe-area-inset-left);
}

/* ===== Header / Footer ===== */
.app-header {
  background: var(--color-primary);
  color: white;
  padding: 1rem 1.25rem;
  text-align: center;
  position: sticky;
  top: 0;
  z-index: 10;
  box-shadow: var(--shadow);
}
.app-header h1 { font-size: 1.25rem; font-weight: 700; }
.app-header .subtitle { font-size: 0.8rem; opacity: 0.85; margin-top: 0.15rem; }

.app-footer {
  text-align: center;
  padding: 1.5rem 1rem 2rem;
}
.app-footer .small { font-size: 0.75rem; }

/* ===== Main / Screen ===== */
main { max-width: 720px; margin: 0 auto; padding: 1rem; min-height: calc(100vh - 130px); }
.screen { display: none; animation: fadeIn 0.25s ease; }
.screen.active { display: block; }
@keyframes fadeIn { from { opacity: 0; transform: translateY(4px); } to { opacity: 1; transform: none; } }

/* ===== Card ===== */
.card {
  background: var(--color-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.5rem 1.25rem;
  margin-bottom: 1rem;
}
.card h2 { font-size: 1.15rem; margin-bottom: 0.75rem; }
.card h3 { font-size: 0.9rem; margin: 1.25rem 0 0.5rem; color: var(--color-muted); font-weight: 600; }
.muted { color: var(--color-muted); font-size: 0.9rem; }

/* ===== Options (Radio) ===== */
.option-group { margin-bottom: 0.5rem; }
.radio {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.65rem 0.85rem;
  margin-bottom: 0.4rem;
  border: 1px solid var(--color-border);
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.15s;
  font-size: 0.95rem;
}
.radio:hover { background: var(--color-tag-bg); }
.radio input[type="radio"] { accent-color: var(--color-primary); cursor: pointer; }
.radio input[type="radio"]:checked + span { font-weight: 600; }

/* ===== Buttons ===== */
.btn-primary, .btn-secondary {
  padding: 0.85rem 1.5rem;
  border: none;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.15s;
  width: 100%;
  margin-top: 1rem;
}
.btn-primary {
  background: var(--color-primary);
  color: white;
}
.btn-primary:hover { background: var(--color-primary-dark); }
.btn-primary:disabled { background: var(--color-muted); cursor: not-allowed; }
.btn-secondary {
  background: transparent;
  color: var(--color-primary);
  border: 1px solid var(--color-primary);
}
.btn-row { display: flex; gap: 0.6rem; margin-top: 1rem; }
.btn-row button { flex: 1; margin-top: 0; }

/* ===== Quiz: progress ===== */
.progress-row {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 0.75rem;
}
#progress-text { font-size: 0.85rem; color: var(--color-muted); min-width: 60px; }
.progress-bar {
  flex: 1;
  height: 6px;
  background: var(--color-border);
  border-radius: 3px;
  overflow: hidden;
}
#progress-fill {
  height: 100%;
  background: var(--color-primary);
  transition: width 0.3s ease;
}

/* ===== Quiz: meta tags ===== */
.qmeta { display: flex; flex-wrap: wrap; gap: 0.4rem; margin-bottom: 0.75rem; }
.tag {
  background: var(--color-tag-bg);
  color: var(--color-tag-text);
  padding: 0.15rem 0.6rem;
  border-radius: 99px;
  font-size: 0.72rem;
  font-weight: 600;
}
.tag.mono { font-family: ui-monospace, "SF Mono", Menlo, Consolas, monospace; }

/* ===== Quiz: question / choices ===== */
#question-text { font-size: 1.05rem; line-height: 1.7; margin-bottom: 1.25rem; }

.choices { display: flex; flex-direction: column; gap: 0.5rem; }
.choice-btn {
  text-align: left;
  padding: 0.85rem 1rem;
  background: var(--color-card);
  border: 1.5px solid var(--color-border);
  border-radius: 8px;
  font-size: 0.95rem;
  color: var(--color-text);
  cursor: pointer;
  transition: all 0.15s;
  display: flex;
  align-items: flex-start;
  gap: 0.7rem;
  font-family: inherit;
  line-height: 1.5;
}
.choice-btn:hover:not(.disabled) {
  border-color: var(--color-primary);
  background: var(--color-tag-bg);
}
.choice-btn .choice-letter {
  flex-shrink: 0;
  width: 1.6rem;
  height: 1.6rem;
  background: var(--color-border);
  color: var(--color-text);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 600;
  font-size: 0.85rem;
}
.choice-btn.disabled { cursor: default; opacity: 0.85; }
.choice-btn.correct {
  border-color: var(--color-success);
  background: var(--color-success-bg);
}
.choice-btn.correct .choice-letter {
  background: var(--color-success);
  color: white;
}
.choice-btn.incorrect {
  border-color: var(--color-danger);
  background: var(--color-danger-bg);
}
.choice-btn.incorrect .choice-letter {
  background: var(--color-danger);
  color: white;
}

/* ===== Explanation ===== */
.explanation {
  margin-top: 1.25rem;
  padding: 1rem;
  background: var(--color-tag-bg);
  border-left: 3px solid var(--color-primary);
  border-radius: 6px;
  font-size: 0.92rem;
  line-height: 1.65;
}
.explanation .label {
  font-weight: 700;
  color: var(--color-primary);
  display: block;
  margin-bottom: 0.4rem;
  font-size: 0.85rem;
}
.row-end { display: flex; justify-content: flex-end; }
.hidden { display: none !important; }

/* ===== Result ===== */
.score {
  text-align: center;
  margin: 1.5rem 0;
}
.score .big {
  font-size: 3rem;
  font-weight: 700;
  color: var(--color-primary);
  display: block;
  line-height: 1;
}
.score .small-label {
  font-size: 0.9rem;
  color: var(--color-muted);
  margin-top: 0.5rem;
  display: block;
}
.score-bar {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.5rem;
  margin: 1rem 0;
}
.score-cell {
  padding: 0.85rem;
  border-radius: 8px;
  text-align: center;
}
.score-cell.correct { background: var(--color-success-bg); color: var(--color-success); }
.score-cell.incorrect { background: var(--color-danger-bg); color: var(--color-danger); }
.score-cell .num { font-size: 1.5rem; font-weight: 700; }
.score-cell .lbl { font-size: 0.8rem; }

/* ===== Review List ===== */
.review-item {
  padding: 1rem;
  border: 1px solid var(--color-border);
  border-radius: 8px;
  margin-bottom: 0.75rem;
}
.review-item .qtext { font-weight: 600; margin-bottom: 0.5rem; font-size: 0.95rem; }
.review-item .answer-row { font-size: 0.85rem; margin: 0.25rem 0; }
.review-item .answer-row .ng { color: var(--color-danger); }
.review-item .answer-row .ok { color: var(--color-success); }
.review-item .expl { font-size: 0.85rem; color: var(--color-muted); margin-top: 0.5rem; line-height: 1.55; }

/* ===== Stats ===== */
.stats {
  margin-top: 1rem;
  padding: 0.75rem;
  background: var(--color-bg);
  border-radius: 8px;
  font-size: 0.85rem;
  color: var(--color-muted);
  text-align: center;
}
.stats:empty { display: none; }

/* ===== Responsive ===== */
@media (min-width: 600px) {
  .card { padding: 1.75rem; }
  #question-text { font-size: 1.1rem; }
}