:root {
    --page-font-family: 'Noto Sans JP', 'Hiragino Kaku Gothic ProN', 'Yu Gothic', 'Segoe UI', sans-serif;
    --page-bg: #f4f6fb;
    --page-header-bg: linear-gradient(135deg, #f8fafc, #eef2ff);
    --page-header-border: rgba(148, 163, 184, 0.24);
    --page-header-shadow: 0 12px 30px rgba(15, 23, 42, 0.08);
    --page-header-padding: 1.5rem 1rem;
    --page-header-padding-sm: 1.25rem 0.75rem;
    --page-header-radius: 1rem;
    --page-title-size: clamp(1.85rem, 1.2vw + 1.4rem, 2.4rem);
    --page-title-size-sm: 1.75rem;
    --page-subtitle-size: clamp(0.98rem, 0.15vw + 0.92rem, 1.08rem);
    --page-eyebrow-size: 0.75rem;
    --page-text: #0f172a;
    --page-muted: #64748b;
}

body.page-theme {
    background: var(--page-bg);
    color: var(--page-text);
    font-family: var(--page-font-family);
}

.page-header {
    max-width: 900px;
    margin: 1.5rem auto 1.5rem;
    padding: var(--page-header-padding);
    border-radius: var(--page-header-radius);
    border: 1px solid var(--page-header-border);
    background: var(--page-header-bg);
    box-shadow: var(--page-header-shadow);
}

.page-header__eyebrow {
    margin: 0 0 0.5rem;
    letter-spacing: 0.2em;
    font-size: var(--page-eyebrow-size);
    font-weight: 600;
    color: var(--page-muted);
    text-transform: uppercase;
}

.page-header__title {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    flex-wrap: wrap;
    gap: 0.65rem;
    margin: 0 0 0.5rem;
    font-size: var(--page-title-size);
    line-height: 1.3;
    letter-spacing: 0.01em;
    color: #111827;
}

.page-header__subtitle {
    margin: 0;
    color: var(--page-muted);
    font-size: var(--page-subtitle-size);
    line-height: 1.7;
}

.page-header__title-link {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 2.25rem;
    height: 2.25rem;
    border-radius: 50%;
    font-size: 0.7em;
    color: var(--bs-primary);
    background-color: rgba(13, 110, 253, 0.1);
    transition: color 0.2s ease, background-color 0.2s ease, opacity 0.2s ease;
    text-decoration: none;
}

.page-header__title-link:hover,
.page-header__title-link:focus {
    color: #0a58ca;
    background-color: rgba(13, 110, 253, 0.2);
    text-decoration: none;
}

@media (max-width: 576px) {
    .page-header {
        margin-top: 1.25rem;
        padding: var(--page-header-padding-sm);
    }

    .page-header__title {
        font-size: var(--page-title-size-sm);
    }
}