/* ---------------------------------------------------------
   なんでなの？図鑑 共通スタイル
   - 子ども向け教育辞典サイト
   - 白背景 + 淡い黄・青・緑のアクセント
   - 本文16px以上 / 行間1.7前後 / 強めのコントラスト
   --------------------------------------------------------- */

:root {
  --bg: #ffffff;
  --bg-soft: #f7f9fb;
  --ink: #1f2933;
  --ink-soft: #52606d;
  --line: #e2e6ea;

  --yellow: #f6c945;
  --yellow-surface: #fff8e1;
  --blue: #3a7bd0;
  --blue-surface: #e9f1fb;
  --green: #4f9d63;
  --green-surface: #ecf6ee;

  --radius: 14px;
  --radius-lg: 22px;
  --shadow: 0 2px 10px rgba(31, 41, 51, 0.06);
  --maxw: 960px;

  --font: "Hiragino Kaku Gothic ProN", "Hiragino Sans", "Yu Gothic UI",
    "Yu Gothic", Meiryo, system-ui, -apple-system, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font);
  font-size: 17px;
  line-height: 1.8;
  color: var(--ink);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

img { max-width: 100%; height: auto; }

a { color: var(--blue); text-underline-offset: 2px; }
a:hover { color: #285ea3; }

.container {
  width: 100%;
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: 20px;
}

/* ---- アクセシビリティ：スキップリンク ---- */
.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--ink);
  color: #fff;
  padding: 10px 16px;
  border-radius: 0 0 10px 0;
  z-index: 1000;
}
.skip-link:focus { left: 0; color: #fff; }

:focus-visible {
  outline: 3px solid var(--blue);
  outline-offset: 2px;
  border-radius: 4px;
}

/* ---------------------------------------------------------
   ヘッダー
   --------------------------------------------------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: saturate(1.2) blur(6px);
  border-bottom: 1px solid var(--line);
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  min-height: 64px;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 800;
  font-size: 1.15rem;
  color: var(--ink);
  text-decoration: none;
}
.brand-mark {
  display: inline-grid;
  place-items: center;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: var(--yellow);
  color: #6b4e00;
  font-weight: 900;
  font-size: 1.25rem;
  box-shadow: var(--shadow);
}
.brand-text { letter-spacing: 0.01em; }

.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 44px;
  height: 44px;
  padding: 0;
  background: transparent;
  border: 1px solid var(--line);
  border-radius: 10px;
  cursor: pointer;
}
.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  margin-inline: auto;
  background: var(--ink);
  transition: transform 0.2s ease, opacity 0.2s ease;
}

.site-nav ul {
  display: flex;
  align-items: center;
  gap: 6px;
  margin: 0;
  padding: 0;
  list-style: none;
}
.site-nav a {
  display: inline-block;
  padding: 8px 14px;
  border-radius: 10px;
  color: var(--ink);
  text-decoration: none;
  font-weight: 600;
}
.site-nav a:hover { background: var(--blue-surface); color: var(--ink); }

/* ---------------------------------------------------------
   汎用レイアウト
   --------------------------------------------------------- */
main { display: block; }
.section { padding-block: 40px; }
.section--soft { background: var(--bg-soft); }

h1, h2, h3 { line-height: 1.4; color: var(--ink); }
h1 { font-size: clamp(1.5rem, 4vw, 2.1rem); margin: 0 0 0.4em; }
h2 { font-size: clamp(1.25rem, 3vw, 1.5rem); margin: 1.6em 0 0.6em; }
h3 { font-size: 1.1rem; margin: 1.3em 0 0.4em; }

.lead { font-size: 1.1rem; color: var(--ink-soft); }

.btn {
  display: inline-block;
  padding: 12px 22px;
  border-radius: 999px;
  background: var(--blue);
  color: #fff;
  font-weight: 700;
  text-decoration: none;
  box-shadow: var(--shadow);
}
.btn:hover { background: #2f6abd; color: #fff; }
.btn--ghost {
  background: #fff;
  color: var(--ink);
  border: 1px solid var(--line);
}
.btn--ghost:hover { background: var(--bg-soft); color: var(--ink); }

/* ---------------------------------------------------------
   トップ：ヒーロー
   --------------------------------------------------------- */
.hero {
  background: linear-gradient(180deg, var(--yellow-surface), #fff 80%);
  border-bottom: 1px solid var(--line);
}
.hero-inner { padding-block: 52px; text-align: center; }
.hero h1 { margin-bottom: 0.3em; }
.hero .lead { max-width: 40em; margin-inline: auto; }

/* 検索窓風UI */
.search {
  margin: 26px auto 6px;
  max-width: 540px;
}
.search-field {
  display: flex;
  align-items: center;
  gap: 8px;
  background: #fff;
  border: 2px solid var(--line);
  border-radius: 999px;
  padding: 6px 8px 6px 18px;
  box-shadow: var(--shadow);
}
.search-field:focus-within { border-color: var(--blue); }
.search-field svg { flex: none; }
.search input[type="search"] {
  flex: 1;
  border: 0;
  outline: none;
  font-size: 1rem;
  background: transparent;
  color: var(--ink);
  padding: 8px 0;
}
.search-hint {
  margin-top: 10px;
  font-size: 0.9rem;
  color: var(--ink-soft);
}

/* ---------------------------------------------------------
   カード / グリッド
   --------------------------------------------------------- */
.grid {
  display: grid;
  gap: 16px;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
}
.grid--cats { grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); }

.card {
  display: flex;
  flex-direction: column;
  gap: 6px;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px;
  text-decoration: none;
  color: var(--ink);
  box-shadow: var(--shadow);
  transition: transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease;
}
.card:hover {
  transform: translateY(-3px);
  border-color: var(--blue);
  color: var(--ink);
  box-shadow: 0 8px 18px rgba(31, 41, 51, 0.1);
}
.card .tag { align-self: flex-start; }
.card-title { font-weight: 700; font-size: 1.05rem; }
.card-desc { font-size: 0.92rem; color: var(--ink-soft); margin: 0; }

.card-cat {
  align-items: center;
  text-align: center;
  gap: 8px;
}
.card-cat .cat-emoji { font-size: 1.9rem; }
.card-cat .cat-name { font-weight: 700; }
.card-cat .cat-count { font-size: 0.82rem; color: var(--ink-soft); }

/* タグ / ラベル */
.tag {
  display: inline-block;
  padding: 3px 10px;
  border-radius: 999px;
  font-size: 0.8rem;
  font-weight: 700;
  background: var(--green-surface);
  color: #2f6b3f;
}
.tag--cat { background: var(--blue-surface); color: #28568f; }
.tag--grade { background: var(--yellow-surface); color: #8a6400; }

/* リスト見出し */
.section-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 16px;
}
.section-head h2 { margin: 0; }
.section-head .more { font-weight: 700; font-size: 0.95rem; }

/* 検索の「見つからない」メッセージ */
.no-result {
  display: none;
  padding: 18px;
  border: 1px dashed var(--line);
  border-radius: var(--radius);
  color: var(--ink-soft);
  text-align: center;
}

/* ---------------------------------------------------------
   パンくず
   --------------------------------------------------------- */
.breadcrumb {
  font-size: 0.88rem;
  color: var(--ink-soft);
  padding-block: 14px;
}
.breadcrumb ol {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin: 0;
  padding: 0;
  list-style: none;
}
.breadcrumb li { display: flex; align-items: center; gap: 6px; }
.breadcrumb li + li::before { content: "›"; color: var(--line); }
.breadcrumb a { color: var(--ink-soft); text-decoration: none; }
.breadcrumb a:hover { text-decoration: underline; }

/* ---------------------------------------------------------
   記事
   --------------------------------------------------------- */
.article { padding-block: 8px 48px; }
.article-header { margin-bottom: 8px; }
.article-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 14px;
}
.article-body { font-size: 1.05rem; }
.article-body p { margin: 0 0 1.1em; }
.article-body section { margin-bottom: 8px; }
.article-body ul, .article-body ol { padding-left: 1.4em; }
.article-body li { margin-bottom: 0.4em; }

.article-body section > h2 {
  display: flex;
  align-items: center;
  gap: 10px;
}
.article-body section > h2::before {
  content: "";
  width: 8px;
  height: 22px;
  border-radius: 4px;
  background: var(--yellow);
}

/* まず答え */
.answer-box {
  background: var(--yellow-surface);
  border: 1px solid #f0dca0;
  border-radius: var(--radius-lg);
  padding: 20px 22px;
  margin: 6px 0 22px !important;
}
.answer-box > h2 { margin-top: 0; }
.answer-box > h2::before { background: var(--yellow); }
.answer-box p { font-size: 1.12rem; font-weight: 600; margin-bottom: 0; }

/* おうちの人・先生へ */
.parent-note {
  background: var(--blue-surface);
  border: 1px solid #cfe0f4;
  border-radius: var(--radius);
  padding: 18px 20px;
  margin: 26px 0 !important;
}
.parent-note > h2 { margin-top: 0; }
.parent-note > h2::before { background: var(--blue); }
.parent-note p { font-size: 0.98rem; color: #324a63; }

/* ミニクイズ */
.quiz-box {
  background: var(--green-surface);
  border: 1px solid #cfe7d4;
  border-radius: var(--radius);
  padding: 18px 20px;
  margin: 26px 0 !important;
}
.quiz-box > h2 { margin-top: 0; }
.quiz-box > h2::before { background: var(--green); }
.quiz-box .quiz-q { font-weight: 700; }
.quiz-box details {
  margin-top: 10px;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 10px 14px;
}
.quiz-box summary {
  cursor: pointer;
  font-weight: 700;
  color: var(--green);
}
.quiz-box details[open] summary { margin-bottom: 8px; }

/* 参考 / 免責 */
.sources {
  margin-top: 28px;
  padding-top: 16px;
  border-top: 1px solid var(--line);
  font-size: 0.92rem;
  color: var(--ink-soft);
}
.sources h2 { font-size: 1.05rem; }
.sources h2::before { display: none; }

.disclaimer {
  margin-top: 18px;
  font-size: 0.82rem;
  color: var(--ink-soft);
}

/* 関連するなぜ */
.related { margin-top: 36px; }
.related h2 { font-size: 1.2rem; }

/* 上へ戻る */
.to-top {
  position: fixed;
  right: 16px;
  bottom: 16px;
  width: 48px;
  height: 48px;
  display: grid;
  place-items: center;
  background: var(--ink);
  color: #fff;
  border: 0;
  border-radius: 50%;
  font-size: 1.2rem;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.2s ease, visibility 0.2s ease;
  box-shadow: var(--shadow);
  z-index: 90;
}
.to-top.is-visible { opacity: 1; visibility: visible; }
.to-top:hover { background: #000; }

/* ---------------------------------------------------------
   固定ページ（about / contact / privacy）
   --------------------------------------------------------- */
.page { padding-block: 8px 48px; }
.page h2::before {
  content: "";
  display: inline-block;
  width: 8px;
  height: 20px;
  margin-right: 10px;
  vertical-align: -3px;
  border-radius: 4px;
  background: var(--green);
}
.info-table {
  width: 100%;
  border-collapse: collapse;
  margin: 16px 0;
}
.info-table th, .info-table td {
  text-align: left;
  vertical-align: top;
  padding: 12px 14px;
  border: 1px solid var(--line);
}
.info-table th {
  width: 34%;
  background: var(--bg-soft);
  font-weight: 700;
  white-space: nowrap;
}
.callout {
  background: var(--yellow-surface);
  border: 1px solid #f0dca0;
  border-radius: var(--radius);
  padding: 16px 18px;
  margin: 18px 0;
}

/* 比較表（水のちがい記事など） */
.table-wrap { overflow-x: auto; margin: 16px 0; }
.compare-table {
  width: 100%;
  min-width: 560px;
  border-collapse: collapse;
  font-size: 0.95rem;
}
.compare-table th, .compare-table td {
  border: 1px solid var(--line);
  padding: 10px 12px;
  text-align: left;
  vertical-align: top;
}
.compare-table thead th { background: var(--blue-surface); color: #28568f; }
.compare-table tbody th { background: var(--bg-soft); white-space: nowrap; }

/* ---------------------------------------------------------
   フッター
   --------------------------------------------------------- */
.site-footer {
  margin-top: 40px;
  background: var(--ink);
  color: #cfd6dd;
  padding-block: 30px;
}
.site-footer a { color: #fff; }
.footer-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 20px;
  margin-bottom: 14px;
}
.footer-nav a { text-decoration: none; font-weight: 600; }
.footer-nav a:hover { text-decoration: underline; }
.footer-note { font-size: 0.86rem; color: #aab4bd; margin: 0 0 10px; }
.copyright { font-size: 0.82rem; color: #8c97a1; margin: 0; }

/* ---------------------------------------------------------
   レスポンシブ（スマホ）
   --------------------------------------------------------- */
@media (max-width: 720px) {
  body { font-size: 16px; }
  .nav-toggle { display: flex; }
  .site-nav {
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: #fff;
    border-bottom: 1px solid var(--line);
    box-shadow: var(--shadow);
    display: none;
  }
  .site-nav.is-open { display: block; }
  .site-nav ul {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 8px;
  }
  .site-nav a { padding: 14px 12px; border-radius: 10px; }
  .nav-toggle[aria-expanded="true"] span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
  .nav-toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
  .nav-toggle[aria-expanded="true"] span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

  .hero-inner { padding-block: 38px; }
  .section { padding-block: 30px; }
  .info-table th { width: auto; white-space: normal; }
}

@media (prefers-reduced-motion: reduce) {
  * { scroll-behavior: auto; }
  .card { transition: none; }
}