:root {
  --c-bg: #ffffff;
  --c-bg-alt: #f4f8fc;
  --c-ink: #111111;
  --c-ink-sub: #4a4a4a;
  --c-line: #1a3a5a;
  --c-accent: #cfe0f0;
  --c-accent-deep: #6b8eae;
  --maxw: 880px;
  --pad-x: 24px;
  --serif: "游明朝", "YuMincho", "Hiragino Mincho ProN", "Yu Mincho", "MS PMincho", serif;
}

* {
  box-sizing: border-box;
}

/* i18n 翻訳完了まで非表示（FOUC防止） */
body {
  opacity: 0;
}
body.lang-ready {
  opacity: 1;
  transition: opacity 0.12s ease;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--c-bg);
  color: var(--c-ink);
  font-family: var(--serif);
  font-size: 16px;
  line-height: 1.9;
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--c-ink);
  text-decoration: none;
  border-bottom: 1px solid var(--c-accent-deep);
}
a:hover {
  color: var(--c-accent-deep);
}

/* ── header ─────────────────────────────────────── */
.hdr {
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(255, 255, 255, 0.92);
  border-bottom: 1px solid var(--c-accent);
  backdrop-filter: saturate(140%) blur(4px);
}
.hdr-inner {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 14px var(--pad-x);
  display: flex;
  align-items: baseline;
  gap: 24px;
  flex-wrap: wrap;
}
.brand {
  border: 0;
  display: flex;
  flex-direction: column;
  line-height: 1.2;
  margin-right: auto;
}
.brand > span:first-child {
  font-size: 18px;
  letter-spacing: 0.15em;
}
.brand-sub {
  font-size: 11px;
  color: var(--c-ink-sub);
  letter-spacing: 0.2em;
}

.nav {
  display: flex;
  gap: 18px;
  flex-wrap: wrap;
}
.nav a {
  border: 0;
  font-size: 14px;
  letter-spacing: 0.12em;
  color: var(--c-ink-sub);
}
.nav a:hover {
  color: var(--c-line);
}
.nav a.is-active {
  color: var(--c-line);
  border-bottom: 1px solid var(--c-line);
}

.lang {
  font-size: 12px;
  letter-spacing: 0.12em;
  display: flex;
  align-items: center;
  gap: 6px;
  color: var(--c-ink-sub);
}
.lang button {
  background: transparent;
  border: 0;
  color: inherit;
  font-family: inherit;
  font-size: inherit;
  cursor: pointer;
  padding: 2px 4px;
}
.lang button.is-active {
  color: var(--c-line);
  border-bottom: 1px solid var(--c-line);
}

/* ── hero（トップページ専用）────────────────────── */
.hero {
  padding: 96px var(--pad-x) 72px;
  text-align: center;
  position: relative;
  background: linear-gradient(180deg, var(--c-bg) 0%, var(--c-bg-alt) 100%);
}
.hero-inner {
  max-width: var(--maxw);
  margin: 0 auto;
}
.hero-eyebrow {
  font-size: 12px;
  letter-spacing: 0.4em;
  color: var(--c-accent-deep);
  margin: 0 0 24px;
}
.hero-title {
  font-size: clamp(28px, 5vw, 44px);
  line-height: 1.6;
  letter-spacing: 0.08em;
  margin: 0 0 32px;
  font-weight: 500;
}
.hero-title span {
  display: block;
}
.hero-lead {
  font-size: 15px;
  color: var(--c-ink-sub);
  max-width: 600px;
  margin: 0 auto 0;
}
.hero-rule {
  width: 1px;
  height: 56px;
  background: var(--c-line);
  margin: 40px auto 0;
}

/* ── ページヘッダー（内部ページ共通）────────────── */
.page-hdr {
  padding: 56px var(--pad-x) 40px;
  text-align: center;
  background: linear-gradient(180deg, var(--c-bg) 0%, var(--c-bg-alt) 100%);
  border-bottom: 1px solid var(--c-accent);
}
.page-hdr-eyebrow {
  font-size: 12px;
  letter-spacing: 0.4em;
  color: var(--c-accent-deep);
  margin: 0 0 12px;
}
.page-hdr-title {
  font-size: clamp(22px, 4vw, 34px);
  letter-spacing: 0.1em;
  font-weight: 500;
  margin: 0;
}

/* ── ボタン ──────────────────────────────────────── */
.btn {
  display: inline-block;
  border: 1px solid var(--c-line);
  padding: 12px 28px;
  font-size: 14px;
  letter-spacing: 0.2em;
  color: var(--c-line);
  background: transparent;
  transition: background 0.15s ease, color 0.15s ease;
}
.btn:hover {
  background: var(--c-line);
  color: #fff;
}

/* ── セクション共通 ──────────────────────────────── */
.sec {
  padding: 72px var(--pad-x);
}
.sec-alt {
  background: var(--c-bg-alt);
}
.sec-inner {
  max-width: var(--maxw);
  margin: 0 auto;
}
.sec-num {
  font-size: 13px;
  letter-spacing: 0.4em;
  color: var(--c-accent-deep);
  margin: 0 0 8px;
}
.sec-title {
  font-size: 26px;
  letter-spacing: 0.12em;
  font-weight: 500;
  margin: 0 0 32px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--c-line);
}
.sec-body p {
  margin: 0 0 18px;
}
.sec-intro {
  margin: 0 0 32px;
  font-size: 15px;
  color: var(--c-ink-sub);
}
.bullets {
  margin: 24px 0 0;
  padding: 0;
  list-style: none;
}
.bullets li {
  position: relative;
  padding: 6px 0 6px 24px;
  border-bottom: 1px dotted var(--c-accent-deep);
}
.bullets li::before {
  content: "—";
  position: absolute;
  left: 0;
  color: var(--c-accent-deep);
}

/* ── クイックナビカード（index専用）────────────── */
.quicknav-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 16px;
  margin-top: 8px;
}
.quicknav-card {
  border: 1px solid var(--c-accent);
  padding: 20px;
  display: block;
  transition: border-color 0.15s ease, background 0.15s ease;
}
.quicknav-card:hover {
  border-color: var(--c-accent-deep);
  background: #fff;
  color: var(--c-ink);
}
.quicknav-title {
  margin: 0 0 6px;
  font-size: 15px;
  letter-spacing: 0.1em;
  font-weight: 500;
  color: var(--c-line);
}
.quicknav-desc {
  margin: 0;
  font-size: 13px;
  color: var(--c-ink-sub);
  line-height: 1.6;
}

/* ── 外部リンクカード ────────────────────────────── */
.ext-link-card {
  display: block;
  margin-top: 32px;
  padding: 24px;
  background: #fff;
  border: 1px solid var(--c-accent);
  border-left: 4px solid var(--c-line);
  transition: border-color 0.15s ease, background 0.15s ease;
  color: var(--c-ink);
}
.ext-link-card:hover {
  border-color: var(--c-accent-deep);
  border-left-color: var(--c-line);
  background: var(--c-bg-alt);
}
.ext-link-title {
  margin: 0 0 8px;
  font-size: 16px;
  letter-spacing: 0.1em;
  font-weight: 500;
  color: var(--c-line);
}
.ext-link-title::after {
  content: " ↗";
  font-size: 12px;
}
.ext-link-desc {
  margin: 0 0 10px;
  font-size: 13px;
  color: var(--c-ink-sub);
  line-height: 1.7;
}
.ext-link-cta {
  margin: 0;
  font-size: 13px;
  letter-spacing: 0.12em;
  color: var(--c-accent-deep);
}

/* ── チーム ──────────────────────────────────────── */
.team-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 32px;
}
.member {
  background: #fff;
  border: 1px solid var(--c-accent);
  padding: 32px 24px;
  text-align: center;
}
.member-photo {
  width: 100px;
  height: 100px;
  border-radius: 50%;
  overflow: hidden;
  margin: 0 auto 16px;
  border: 2px solid var(--c-accent);
}
.member-photo img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}
.member-name {
  margin: 0 0 6px;
  font-size: 18px;
  letter-spacing: 0.08em;
  font-weight: 500;
}
.member-role {
  margin: 0 0 4px;
  font-size: 13px;
  color: var(--c-accent-deep);
  letter-spacing: 0.08em;
}
.member-aff {
  margin: 0 0 12px;
  font-size: 13px;
  color: var(--c-ink-sub);
}
.member-bio {
  margin: 0;
  font-size: 14px;
  color: var(--c-ink-sub);
  line-height: 1.7;
  text-align: left;
}

/* ── 実験カード ──────────────────────────────────── */
.exp-grid {
  display: grid;
  gap: 24px;
}
.exp-card {
  border: 1px solid var(--c-accent);
  padding: 24px;
  display: grid;
  grid-template-columns: 100px 1fr;
  gap: 0 24px;
  align-items: start;
  background: #fff;
}
.exp-card-date {
  font-size: 13px;
  letter-spacing: 0.12em;
  color: var(--c-accent-deep);
  padding-top: 4px;
}
.exp-card-title {
  margin: 0 0 8px;
  font-size: 20px;
  letter-spacing: 0.08em;
  font-weight: 500;
}
.exp-card-desc {
  margin: 0 0 16px;
  font-size: 14px;
  color: var(--c-ink-sub);
  line-height: 1.7;
}
.exp-card-link {
  font-size: 13px;
  letter-spacing: 0.1em;
}
.exp-coming {
  margin-top: 32px;
  font-size: 14px;
  color: var(--c-ink-sub);
  padding: 20px;
  border: 1px dashed var(--c-accent-deep);
  text-align: center;
}

/* ── セッション詳細ページ ────────────────────────── */
.session-back {
  display: inline-block;
  font-size: 13px;
  letter-spacing: 0.1em;
  color: var(--c-ink-sub);
  margin-bottom: 32px;
  border: 0;
}
.session-back:hover {
  color: var(--c-line);
}
.flow-list {
  margin: 16px 0 0;
  padding: 0;
  list-style: none;
  counter-reset: flow;
}
.flow-list li {
  counter-increment: flow;
  position: relative;
  padding: 10px 0 10px 48px;
  border-bottom: 1px dotted var(--c-accent-deep);
  font-size: 15px;
}
.flow-list li::before {
  content: counter(flow);
  position: absolute;
  left: 0;
  top: 10px;
  width: 28px;
  height: 28px;
  background: var(--c-accent);
  color: var(--c-line);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 13px;
  letter-spacing: 0;
}
.photos-placeholder {
  margin-top: 16px;
  background: var(--c-bg-alt);
  border: 1px dashed var(--c-accent-deep);
  padding: 48px 24px;
  text-align: center;
  color: var(--c-ink-sub);
  font-size: 14px;
}

/* ── 学術報告 ────────────────────────────────────── */
.reports-empty {
  margin-top: 16px;
  padding: 48px 24px;
  background: var(--c-bg-alt);
  border: 1px solid var(--c-accent);
  text-align: center;
  font-size: 14px;
  color: var(--c-ink-sub);
}

/* ── meta dl ─────────────────────────────────────── */
.meta {
  display: grid;
  grid-template-columns: 100px 1fr;
  gap: 8px 20px;
  margin: 24px 0;
  padding: 20px;
  border-top: 1px solid var(--c-line);
  border-bottom: 1px solid var(--c-line);
}
.meta dt {
  font-size: 13px;
  letter-spacing: 0.2em;
  color: var(--c-accent-deep);
}
.meta dd {
  margin: 0;
  font-size: 15px;
}

/* ── お問い合わせフォーム ────────────────────────── */
.form-wrap {
  margin-top: 32px;
  background: #fff;
  border: 1px solid var(--c-accent);
  padding: 16px;
}
.form-wrap iframe {
  display: block;
  width: 100%;
  border: 0;
  background: var(--c-bg-alt);
}
.form-note {
  font-size: 13px;
  color: var(--c-ink-sub);
  margin: 12px 0 0;
}

/* ── FAQ ─────────────────────────────────────────── */
.faq details {
  border-bottom: 1px solid var(--c-accent-deep);
  padding: 16px 0;
}
.faq summary {
  cursor: pointer;
  font-size: 16px;
  letter-spacing: 0.06em;
  list-style: none;
  position: relative;
  padding-left: 24px;
}
.faq summary::-webkit-details-marker {
  display: none;
}
.faq summary::before {
  content: "問";
  position: absolute;
  left: 0;
  color: var(--c-accent-deep);
  font-size: 13px;
}
.faq details[open] summary::before {
  content: "答";
  color: var(--c-line);
}
.faq p {
  margin: 12px 0 0 24px;
  color: var(--c-ink-sub);
  font-size: 15px;
}

/* ── メール連絡 ──────────────────────────────────── */
.mail-block {
  margin-top: 16px;
  padding: 24px;
  background: #fff;
  border: 1px solid var(--c-accent);
}
.mail-block p {
  margin: 0;
  font-size: 15px;
  line-height: 1.8;
}

/* ── footer ──────────────────────────────────────── */
.ftr {
  border-top: 1px solid var(--c-line);
  padding: 40px var(--pad-x);
  text-align: center;
  background: #fff;
}
.ftr-inner {
  max-width: var(--maxw);
  margin: 0 auto;
}
.ftr-brand {
  margin: 0 0 8px;
  font-size: 14px;
  letter-spacing: 0.3em;
}
.ftr-meta {
  margin: 0 0 8px;
  font-size: 13px;
  color: var(--c-ink-sub);
}

/* ── レスポンシブ ────────────────────────────────── */
@media (max-width: 600px) {
  .hdr-inner {
    gap: 12px;
  }
  .nav {
    gap: 10px;
    width: 100%;
    order: 3;
  }
  .nav a {
    font-size: 13px;
  }
  .meta {
    grid-template-columns: 80px 1fr;
    padding: 16px;
  }
  .sec {
    padding: 56px var(--pad-x);
  }
  .hero {
    padding: 64px var(--pad-x) 48px;
  }
  .exp-card {
    grid-template-columns: 1fr;
  }
  .exp-card-date {
    padding-top: 0;
  }
}