/* 共通CSS */

/* CSS変数 */
:root {
    --color-primary: #0c3388;
    --color-primary-dark: #071e52;
    --color-primary-light: #1a4fad;
    --color-accent: #2d7dd2;
    --color-accent-light: #5ca0e8;
    --color-text: #1a1a1a;
    --color-text-light: #4a4a4a;
    --color-text-muted: #8a8a8a;
    --color-bg: #ffffff;
    --color-bg-gray: #f7f8fa;
    --color-bg-dark: #0a0f1a;
    --color-bg-darker: #060a12;
    --color-border: #e0e4eb;
    --color-border-light: #eef1f5;
    --color-challenge: #c2955a;
    --color-category-media: #6b5b95;
    --color-category-paper: #b8860b;
    --color-gray-medium: #e8eaed;
    --font-sans: "Noto Sans JP", -apple-system, BlinkMacSystemFont, sans-serif;
    --font-serif: "Noto Serif JP", Georgia, serif;
    --font-latin: "Lato", sans-serif;
    --section-padding: 160px;
    --section-padding-md: 120px;
    --section-padding-sm: 80px;
    --container-width: 1280px;
    --container-narrow: 960px;
    --transition: 0.4s cubic-bezier(0.4, 0.4, 0, 1);
    --transition-fast: 0.25s ease;
}

/* ベーススタイル */
body {
    font-family: var(--font-sans);
    font-weight: 400;
    line-height: 1.9;
    color: var(--color-text);
    background-color: var(--color-bg);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}
a {
    transition: all var(--transition-fast);
}

/* コンテナ */
.container {
    margin: 0 auto;
}
.container-narrow {
    max-width: var(--container-narrow);
}

/* セクション */
.section-gray {
    background-color: var(--color-bg-gray);
}
.section-dark {
    background-color: var(--color-bg-dark);
    color: var(--color-bg);
}
.section-primary {
    background-color: var(--color-primary);
    color: var(--color-bg);
}

/* セクション見出し */
.section_header {
    text-align: left;
}
.section_header-center {
    text-align: center;
}
.section_label {
    display: inline-block;
    font-family: var(--font-latin);
    font-size: 0.6875rem;
    font-weight: 700;
    letter-spacing: 0.3em;
    text-transform: uppercase;
    color: var(--color-primary);
    margin-bottom: 10px;
}
.section-dark .section_label,
.section-primary .section_label {
    color: var(--color-accent-light);
}
.section_title {
    font-family: var(--font-serif);
    font-weight: 500;
    line-height: 1.5;
    color: var(--color-text);
    letter-spacing: 0.04em;
}
.section-dark .section_title,
.section-primary .section_title {
    color: var(--color-bg);
}
.section_lead {
    font-size: 0.9375rem;
    line-height: 2;
    color: var(--color-text-light);
    margin-top: 28px;
    max-width: 640px;
}
.section_header-center .section_lead {
    margin-left: auto;
    margin-right: auto;
}
.section-dark .section_lead,
.section-primary .section_lead {
    color: rgba(255, 255, 255, 0.7);
}

/* ボタン */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 20px 48px;
    font-size: 0.875rem;
    font-weight: 500;
    letter-spacing: 0.08em;
    border: none;
    cursor: pointer;
    transition: all var(--transition);
}
.btn:hover {
    opacity: 1;
}
.btn-primary {
    background-color: var(--color-primary);
    color: var(--color-bg);
}
.btn-primary:hover {
    background-color: var(--color-primary-light);
}
.btn-accent {
    background-color: var(--color-accent);
    color: var(--color-bg);
}
.btn-accent:hover {
    background-color: var(--color-accent-light);
}
.btn-outline {
    background-color: transparent;
    color: var(--color-text);
    border: 1px solid var(--color-text);
}
.btn-outline:hover {
    background-color: var(--color-text);
    color: var(--color-bg);
}
.btn-white {
    background-color: var(--color-bg);
    color: var(--color-primary);
}
.btn-white:hover {
    background-color: var(--color-bg-gray);
}
.btn-ghost {
    background-color: transparent;
    color: var(--color-bg);
    border: 1px solid rgba(255, 255, 255, 0.4);
}
.btn-ghost:hover {
    background-color: rgba(255, 255, 255, 0.1);
    border-color: rgba(255, 255, 255, 0.6);
}
.btn_arrow {
    margin-left: 16px;
    transition: transform var(--transition-fast);
}
.btn:hover .btn_arrow {
    transform: translateX(4px);
}

/* リンク（もっと見る） */
.link_more {
    display: inline-flex;
    align-items: center;
    font-family: var(--font-latin);
    font-size: 0.75rem;
    font-weight: 700;
    color: var(--color-text);
    letter-spacing: 0.1em;
}
.link_more::after {
    content: '\2192';
    margin-left: 12px;
    transition: transform var(--transition-fast);
}
.link_more:hover {
    color: var(--color-accent);
}
.link_more:hover::after {
    transform: translateX(4px);
}

/* ヘッダー */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background-color: transparent;
    transition: background-color var(--transition), box-shadow var(--transition);
}
.header.is_scrolled {
    background-color: rgba(255, 255, 255, 0.98);
    box-shadow: 0 1px 0 var(--color-border);
}
/* 白背景ヘッダー（記事詳細ページ用） */
.page_white_header .header {
    background-color: rgba(255, 255, 255, 0.98);
    box-shadow: 0 1px 0 var(--color-border);
}
.page_white_header .header_logo_main {
    color: var(--color-text);
}
.page_white_header .header_logo_sub {
    color: var(--color-text-muted);
}
.page_white_header .header_nav_link {
    color: var(--color-text);
}
.page_white_header .header_nav_link:hover {
    color: var(--color-accent);
}
.page_white_header .header_hamburger::before,
.page_white_header .header_hamburger::after,
.page_white_header .header_hamburger span {
    background-color: var(--color-text);
}
.header .container {
    max-width: none;
    padding: 0 40px;
}
.header_inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    transition: height var(--transition);
}
.header_logo {
    display: flex;
    flex-direction: column;
    line-height: 1.5;
}
.header_logo_main {
    font-family: var(--font-latin);
    font-size: 1.375rem;
    font-weight: 700;
    color: var(--color-bg);
    letter-spacing: 0.08em;
    white-space: nowrap;
    transition: color var(--transition), font-size var(--transition);
}
.header.is_scrolled .header_logo_main {
    color: var(--color-text);
    font-size: 1.125rem;
}
.header_logo_sub {
    font-size: 0.6875rem;
    font-weight: 400;
    color: rgba(255, 255, 255, 0.5);
    letter-spacing: 0.12em;
    transition: color var(--transition), font-size var(--transition);
}
.header.is_scrolled .header_logo_sub {
    color: var(--color-text-muted);
    font-size: 0.5625rem;
}
.header_nav {
    display: flex;
    align-items: center;
    gap: 32px;
}
.header_nav_link {
    font-size: 0.9375rem;
    font-weight: 500;
    color: rgba(255, 255, 255, 0.85);
    letter-spacing: 0.05em;
    transition: color var(--transition), font-size var(--transition);
}
.header.is_scrolled .header_nav_link {
    color: var(--color-text);
    font-size: 0.8125rem;
}
.header_nav_link:hover {
    color: var(--color-accent-light);
}
.header.is_scrolled .header_nav_link:hover {
    color: var(--color-accent);
}
/* ハンバーガーボタン（PC非表示） */
.header_hamburger {
    display: none;
}
/* SPメニュー内サイト名（PC非表示） */
.header_nav_logo {
    display: none;
}

/* ページヒーロー（2階層目共通） */
.page_hero {
    position: relative;
    background-image: url('../images/common/fv.jpg');
    background-image: image-set(url('../images/common/fv.webp') type('image/webp'), url('../images/common/fv.jpg') type('image/jpeg'));
    background-size: cover;
    background-position: center;
    overflow: hidden;
}
.page_hero::before {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(135deg,
            rgba(6, 10, 18, 0.8) 0%,
            rgba(12, 51, 136, 0.6) 50%,
            rgba(6, 10, 18, 0.75) 100%);
}
.page_hero .container {
    position: relative;
    z-index: 1;
}
.page_hero_inner {
    max-width: 800px;
}
.page_hero_label {
    display: inline-block;
    font-family: var(--font-latin);
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.2em;
    text-transform: uppercase;
    color: var(--color-accent-light);
    margin-bottom: 24px;
}
.page_hero_title {
    font-family: var(--font-serif);
    font-weight: 500;
    line-height: 1.4;
    color: var(--color-bg);
    letter-spacing: 0.06em;
    margin-bottom: 28px;
}
.page_hero_lead {
    font-size: 1rem;
    line-height: 2;
    color: rgba(255, 255, 255, 0.75);
}

/* CTA（共通） */
.cta {
    background-color: var(--color-bg-gray);
}
.cta_inner {
    background-color: var(--color-bg);
}
.cta_content h2 {
    font-family: var(--font-serif);
    font-size: 1.625rem;
    font-weight: 500;
    color: var(--color-text);
    margin-bottom: 16px;
    letter-spacing: 0.04em;
}
.cta_content p {
    font-size: 0.875rem;
    color: var(--color-text-light);
}
.cta_actions {
    display: flex;
    gap: 20px;
    flex-shrink: 0;
}
.cta_actions .btn {
    white-space: nowrap;
}

/* フッター */
.footer {
    background-color: var(--color-bg-dark);
    color: rgba(255, 255, 255, 0.6);
}
.footer_grid {
    border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}
.footer_brand {
    max-width: 300px;
}
.footer_logo {
    font-family: var(--font-latin);
    font-size: 1rem;
    font-weight: 700;
    color: var(--color-bg);
    letter-spacing: 0.15em;
    margin-bottom: 6px;
}
.footer_logo_sub {
    font-family: var(--font-latin);
    font-size: 0.5625rem;
    letter-spacing: 0.25em;
    color: var(--color-accent);
    margin-bottom: 28px;
}
.footer_desc {
    font-size: 0.75rem;
    line-height: 2.2;
    color: rgba(255, 255, 255, 0.35);
}
.footer_nav_title {
    font-family: var(--font-latin);
    font-size: 0.6875rem;
    font-weight: 700;
    color: var(--color-bg);
    margin-bottom: 24px;
    letter-spacing: 0.1em;
}
.footer_nav_list li {
    margin-bottom: 14px;
}
.footer_nav_list a {
    font-size: 0.75rem;
    color: rgba(255, 255, 255, 0.45);
    transition: color var(--transition-fast);
}
.footer_nav_list a:hover {
    color: var(--color-bg);
}
.footer_copyright {
    font-family: var(--font-latin);
    color: rgba(255, 255, 255, 0.25);
    letter-spacing: 0.05em;
}
.footer_links {
    display: flex;
    gap: 32px;
}
.footer_links a {
    color: rgba(255, 255, 255, 0.35);
}
.footer_links a:hover {
    color: var(--color-bg);
}

/* PC/SP表示切替ユーティリティ */
.br_pc { display: none; }
.br_sp { display: inline; }

/* PC */
@media screen and (min-width: 900px) {
    .br_pc { display: inline; }
    .br_sp { display: none; }
    .container {
        max-width: var(--container-width);
        padding: 0 60px;
    }
    .section {
        padding: var(--section-padding) 0;
    }
    .section_header {
        margin-bottom: 80px;
    }
    .section_title {
        font-size: 1.75rem;
    }
    .header_inner {
        height: 100px;
    }
    .header.is_scrolled .header_inner {
        height: 70px;
    }
    .page_hero {
        padding: 180px 0 100px;
    }
    .page_hero_title {
        font-size: 3rem;
    }
    .cta {
        padding: var(--section-padding-md) 0;
    }
    .cta_inner {
        display: flex;
        justify-content: space-between;
        align-items: center;
        padding: 72px 100px;
    }
    .footer {
        padding: 100px 0 48px;
    }
    .footer_grid {
        display: grid;
        grid-template-columns: 1fr 2fr;
        gap: 100px;
        padding-bottom: 80px;
    }
    .footer_nav {
        display: grid;
        grid-template-columns: repeat(4, 1fr);
        gap: 48px;
    }
    .footer_bottom {
        display: flex;
        justify-content: space-between;
        align-items: center;
        padding-top: 48px;
        font-size: 0.6875rem;
    }
}

/* SP */
@media screen and (max-width: 899px) {
    .container {
        padding: 0 20px;
    }
    .section {
        padding: var(--section-padding-sm) 0;
    }
    .section_header {
        margin-bottom: 48px;
    }
    .section_title {
        font-size: 1.375rem;
    }
    .header .container {
        padding: 0 20px;
    }
    .header_hamburger {
        display: block;
        position: relative;
        z-index: 1100;
        width: 32px;
        height: 24px;
        background: none;
        border: none;
        cursor: pointer;
        padding: 0;
    }
    .header_hamburger::before,
    .header_hamburger::after,
    .header_hamburger span {
        content: '';
        display: block;
        position: absolute;
        left: 0;
        width: 100%;
        height: 2px;
        background-color: var(--color-bg);
        transition: transform var(--transition-fast), opacity var(--transition-fast);
    }
    .header.is_scrolled .header_hamburger::before,
    .header.is_scrolled .header_hamburger::after,
    .header.is_scrolled .header_hamburger span {
        background-color: var(--color-text);
    }
    .header_hamburger::before {
        top: 0;
    }
    .header_hamburger span {
        top: 50%;
        transform: translateY(-50%);
    }
    .header_hamburger::after {
        bottom: 0;
    }
    /* ハンバーガー開状態 */
    .header_hamburger.is_open::before {
        top: 50%;
        transform: translateY(-50%) rotate(45deg);
        background-color: var(--color-bg);
    }
    .header_hamburger.is_open span {
        opacity: 0;
    }
    .header_hamburger.is_open::after {
        bottom: 50%;
        transform: translateY(50%) rotate(-45deg);
        background-color: var(--color-bg);
    }
    .header_nav {
        display: flex;
        flex-direction: column;
        align-items: center;
        justify-content: center;
        gap: 32px;
        position: fixed;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        background-color: rgba(6, 10, 18, 0.95);
        z-index: 1050;
        opacity: 0;
        visibility: hidden;
        transition: opacity var(--transition), visibility var(--transition);
    }
    .header_nav.is_open {
        opacity: 1;
        visibility: visible;
    }
    .header_nav_logo {
        display: flex;
        flex-direction: column;
        align-items: center;
        gap: 8px;
        margin-bottom: 16px;
    }
    .header_nav_logo_main {
        font-family: var(--font-latin);
        font-size: 1.25rem;
        font-weight: 700;
        color: var(--color-bg);
        letter-spacing: 0.12em;
    }
    .header_nav_logo_sub {
        font-size: 0.625rem;
        color: rgba(255, 255, 255, 0.4);
        letter-spacing: 0.15em;
    }
    .header_nav_link {
        font-size: 1.125rem;
        color: rgba(255, 255, 255, 0.85);
    }
    .header.is_scrolled .header_nav_link {
        color: rgba(255, 255, 255, 0.85);
        font-size: 1.125rem;
    }
    .header_inner {
        height: 80px;
    }
    .header.is_scrolled .header_inner {
        height: 60px;
    }
    .page_hero {
        padding: 140px 0 60px;
    }
    .page_hero_title {
        font-size: 1.75rem;
    }
    .cta {
        padding: 64px 0;
    }
    .cta_inner {
        display: flex;
        flex-direction: column;
        text-align: center;
        gap: 40px;
        padding: 56px 40px;
    }
    .footer {
        padding: 60px 0 32px;
    }
    .footer_grid {
        display: flex;
        flex-direction: column;
        gap: 48px;
        padding-bottom: 48px;
    }
    .footer_nav {
        display: grid;
        grid-template-columns: repeat(2, 1fr);
        gap: 32px;
    }
    .footer_bottom {
        display: flex;
        flex-direction: column;
        gap: 20px;
        text-align: center;
        padding-top: 32px;
        font-size: 0.6875rem;
    }
}

/* 404ページ */
.error_page {
    padding: 12rem 0 6rem;
    text-align: center;
}
.error_page_inner {
    max-width: 600px;
    margin: 0 auto;
}
.error_page_code {
    font-family: var(--font-latin);
    font-size: 8rem;
    font-weight: 700;
    color: var(--color-border);
    line-height: 1;
    margin-bottom: 1.5rem;
}
.error_page_title {
    font-family: var(--font-serif);
    font-size: 1.5rem;
    font-weight: 500;
    color: var(--color-text);
    margin-bottom: 1.5rem;
}
.error_page_text {
    font-size: 0.9375rem;
    line-height: 2;
    color: var(--color-text-light);
    margin-bottom: 3rem;
}
.error_page_actions {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 4rem;
}
.error_page_nav {
    padding-top: 3rem;
    border-top: 1px solid var(--color-border-light);
}
.error_page_nav_title {
    font-family: var(--font-latin);
    font-size: 0.6875rem;
    font-weight: 700;
    letter-spacing: 0.2em;
    text-transform: uppercase;
    color: var(--color-text-muted);
    margin-bottom: 1.5rem;
}
.error_page_nav_list {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 0.5rem 1.5rem;
}
.error_page_nav_list a {
    font-size: 0.875rem;
    color: var(--color-accent);
    text-decoration: none;
}
.error_page_nav_list a:hover {
    text-decoration: underline;
}
@media screen and (max-width: 899px) {
    .error_page {
        padding: 10rem 0 4rem;
    }
    .error_page_code {
        font-size: 5rem;
    }
    .error_page_title {
        font-size: 1.25rem;
    }
    .error_page_actions {
        flex-direction: column;
        align-items: center;
    }
}