/* 3ページ共通のナビゲーション（一覧 / 2D地図 / 3D地球儀） */
.site-nav { display: inline-flex; gap: 4px; padding: 3px; border-radius: 999px;
  background: var(--nav-bg, #eef2f7); border: 1px solid var(--nav-line, #dbe3ee); }
.site-nav a { padding: 5px 12px; border-radius: 999px; font-size: 0.78rem; font-weight: 600;
  text-decoration: none; color: var(--nav-text, #475569); white-space: nowrap; }
.site-nav a:hover { background: var(--nav-hover, #e2e8f0); }
.site-nav a[aria-current="page"] { background: var(--nav-active, #2563eb); color: #fff; pointer-events: none; }
.site-nav.dark { --nav-bg: rgba(15, 23, 42, 0.86); --nav-line: #243049; --nav-text: #cbd5e1;
  --nav-hover: #1e293b; --nav-active: #38bdf8; }
.site-nav.dark a[aria-current="page"] { color: #0b1220; }
@media (max-width: 480px) { .site-nav a { padding: 5px 9px; font-size: 0.74rem; } }