/**
 * サイト共通ヘッダー（全ページ共通・記事ページ/TOP/一覧で共用）
 * 記事ページ: 上部に固定（sticky）。TOP・一覧: 画面上部に固定（fixed）。
 */
:root { --site-header-h: 52px; }

.site-header {
    position: sticky;
    top: 0;
    z-index: 50;
    height: var(--site-header-h);
    background: color-mix(in srgb, #0a0e1a 82%, transparent);
    -webkit-backdrop-filter: blur(12px);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid color-mix(in srgb, #3e5e9b 25%, transparent);
    font-family: 'Inter', 'Noto Sans JP', -apple-system, BlinkMacSystemFont, sans-serif;
    line-height: 1.4;
}
.site-header--fixed { position: fixed; inset: 0 0 auto 0; }

.site-header__inner {
    display: flex;
    align-items: center;
    gap: 1.5rem;
    height: 100%;
    padding: 0 3.5rem;
}

/* ブランド: ロゴの下にキャッチコピーを小さく添え、2行の横幅をそろえる */
.site-header__brand {
    display: inline-flex;
    flex-direction: column;
    justify-content: center;
    gap: 3px;
    color: #ffffff;
    text-decoration: none;
    line-height: 1;
}
.site-header__brand:hover { text-decoration: none; opacity: 0.85; }
.site-header__logo {
    font-family: 'Orbitron', sans-serif;
    font-size: 2rem;
    font-weight: 900;
    line-height: 0.9;
    letter-spacing: 0.03em;
    color: #ffffff;
}
.site-header__tagline {
    font: 600 0.47rem/1 'Inter', sans-serif;
    letter-spacing: 0.03em;
    text-transform: uppercase;
    color: #ffffff;
    opacity: 0.45;
    white-space: nowrap;
}

.site-header__nav { display: flex; align-items: stretch; height: 100%; margin-left: 0.5rem; }
.site-header__link {
    display: inline-flex;
    align-items: center;
    gap: 0.45rem;
    padding: 0 0.25rem;
    border-bottom: 2px solid transparent;
    font-size: 0.85rem;
    font-weight: 600;
    color: #cbd5e1;
    text-decoration: none;
    transition: color 0.2s, border-color 0.2s;
}
.site-header__link i { font-size: 0.8em; opacity: 0.75; }
.site-header__link:hover { color: #ffffff; text-decoration: none; }
/* 下線はマウスを乗せたときだけ */
.site-header__link:hover { border-bottom-color: var(--accent, #7c3aed); }

.site-header__lang {
    display: inline-flex;
    align-items: center;
    gap: 0.45rem;
    margin-left: auto;
    padding: 0.4rem 1rem;
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: 99px;
    background: rgba(255, 255, 255, 0.06);
    color: #e2e8f0;
    font-size: 0.8rem;
    font-weight: 600;
    letter-spacing: 0.04em;
    text-decoration: none;
    transition: background 0.2s, border-color 0.2s;
}
.site-header__lang:hover {
    background: rgba(255, 255, 255, 0.16);
    border-color: rgba(255, 255, 255, 0.45);
    color: #ffffff;
    text-decoration: none;
}
.site-header__lang i { font-size: 0.85em; opacity: 0.8; }

@media (max-width: 1024px) {
    .site-header__inner { padding: 0 1.25rem; gap: 1rem; }
}
@media (max-width: 420px) {
    .site-header__inner { gap: 0.75rem; }
    .site-header__lang { padding: 0.4rem 0.75rem; }
}
@media (max-width: 360px) {
    .site-header__inner { padding-inline: 0.75rem; gap: 0.5rem; }
    .site-header__nav { margin-left: 0; }
}