:root {
    --background: #f6f7f9;
    --surface: #ffffff;
    --surface-muted: #eef1f5;
    --text: #111318;
    --subtext: #60656f;
    --border: rgba(17, 19, 24, 0.1);
    --accent: #2463eb;
    --accent-dark: #1747b5;
    --header-background: rgba(246, 247, 249, 0.82);
    --shadow: 0 24px 70px rgba(23, 32, 51, 0.08);
    --max-width: 1160px;
}

html[data-theme="dark"] {
    --background: #0d1016;
    --surface: #151922;
    --surface-muted: #11151d;
    --text: #f4f6fa;
    --subtext: #a5acb8;
    --border: rgba(255, 255, 255, 0.1);
    --accent: #7ca6ff;
    --accent-dark: #a8c2ff;
    --header-background: rgba(13, 16, 22, 0.82);
    --shadow: 0 24px 70px rgba(0, 0, 0, 0.3);
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    overflow-x: hidden;
    background: var(--background);
    color: var(--text);
    font-family:
        Inter,
        -apple-system,
        BlinkMacSystemFont,
        "Segoe UI",
        "Hiragino Sans",
        "Hiragino Kaku Gothic ProN",
        "Yu Gothic",
        Meiryo,
        sans-serif;
    line-height: 1.8;
    transition:
        background-color 0.25s ease,
        color 0.25s ease;
}

body.menu-open {
    overflow: hidden;
}

a {
    color: inherit;
    text-decoration: none;
}

button,
a {
    -webkit-tap-highlight-color: transparent;
}

button {
    color: inherit;
    font: inherit;
}

.container {
    width: min(calc(100% - 48px), var(--max-width));
    margin: 0 auto;
}

.site-header {
    position: fixed;
    top: 0;
    left: 0;
    z-index: 100;
    width: 100%;
    border-bottom: 1px solid transparent;
    background: transparent;
    transition:
        background-color 0.25s ease,
        border-color 0.25s ease,
        box-shadow 0.25s ease;
}

.site-header.scrolled {
    border-color: var(--border);
    background: var(--header-background);
    box-shadow: 0 6px 30px rgba(15, 23, 42, 0.04);
    backdrop-filter: blur(20px);
}

.header-inner {
    min-height: 76px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 28px;
}

.site-logo {
    position: relative;
    z-index: 102;
    font-size: 1.08rem;
    font-weight: 750;
    letter-spacing: -0.02em;
}

.desktop-nav {
    display: flex;
    align-items: center;
    gap: 32px;
    color: var(--subtext);
    font-size: 0.92rem;
    font-weight: 600;
}

.desktop-nav a {
    transition: color 0.2s ease;
}

.desktop-nav a:hover {
    color: var(--text);
}

.header-actions {
    position: relative;
    z-index: 102;
    display: flex;
    align-items: center;
    gap: 10px;
}

.theme-button,
.menu-button {
    width: 42px;
    height: 42px;
    border: 1px solid var(--border);
    border-radius: 50%;
    background: var(--surface);
    cursor: pointer;
}

.theme-button {
    display: grid;
    place-items: center;
}

.theme-icon {
    font-size: 1.2rem;
    line-height: 1;
}

.menu-button {
    display: none;
    position: relative;
}

.menu-button span {
    position: absolute;
    left: 12px;
    width: 16px;
    height: 1.5px;
    background: var(--text);
    transition:
        transform 0.25s ease,
        top 0.25s ease;
}

.menu-button span:first-child {
    top: 16px;
}

.menu-button span:last-child {
    top: 23px;
}

.menu-button.active span:first-child {
    top: 20px;
    transform: rotate(45deg);
}

.menu-button.active span:last-child {
    top: 20px;
    transform: rotate(-45deg);
}

.mobile-nav {
    display: none;
}

.hero {
    position: relative;
    min-height: 100vh;
    overflow: hidden;
    display: flex;
    align-items: center;
    padding: 150px 0 80px;
}

.hero-inner {
    position: relative;
    z-index: 2;
}

.hero-decoration {
    position: absolute;
    border-radius: 50%;
    filter: blur(4px);
    pointer-events: none;
}

.hero-decoration-one {
    top: 3%;
    right: -12%;
    width: 580px;
    height: 580px;
    background:
        radial-gradient(
            circle,
            rgba(57, 116, 255, 0.18),
            rgba(57, 116, 255, 0)
        );
}

.hero-decoration-two {
    bottom: -20%;
    left: -15%;
    width: 620px;
    height: 620px;
    background:
        radial-gradient(
            circle,
            rgba(116, 91, 255, 0.12),
            rgba(116, 91, 255, 0)
        );
}

.section-label {
    margin: 0 0 20px;
    color: var(--accent);
    font-size: 0.78rem;
    font-weight: 800;
    letter-spacing: 0.17em;
    text-transform: uppercase;
}

.hero h1 {
    max-width: 1000px;
    margin: 0;
    font-size: clamp(4rem, 10vw, 8.5rem);
    font-weight: 720;
    line-height: 0.94;
    letter-spacing: -0.075em;
}

.hero h1 span {
    display: block;
    color: var(--accent);
}

.hero-description {
    max-width: 770px;
    margin: 42px 0 0;
    color: var(--subtext);
    font-size: clamp(1.05rem, 2vw, 1.3rem);
    line-height: 2;
}

.hero-keywords {
    display: flex;
    flex-wrap: wrap;
    gap: 9px;
    margin-top: 30px;
}

.hero-keywords span {
    padding: 7px 13px;
    border: 1px solid var(--border);
    border-radius: 999px;
    background: rgba(255, 255, 255, 0.3);
    color: var(--subtext);
    font-size: 0.82rem;
    font-weight: 600;
}

html[data-theme="dark"] .hero-keywords span {
    background: rgba(255, 255, 255, 0.025);
}

.hero-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 14px;
    margin-top: 42px;
}

.button {
    min-height: 52px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    padding: 0 24px;
    border: 1px solid var(--border);
    border-radius: 999px;
    font-size: 0.93rem;
    font-weight: 750;
    transition:
        transform 0.2s ease,
        box-shadow 0.2s ease,
        background-color 0.2s ease;
}

.button:hover {
    transform: translateY(-2px);
}

.button-primary {
    border-color: var(--accent);
    background: var(--accent);
    color: #ffffff;
    box-shadow: 0 14px 35px rgba(36, 99, 235, 0.22);
}

.button-primary:hover {
    background: var(--accent-dark);
}

.button-secondary {
    background: var(--surface);
}

.button-secondary:hover {
    box-shadow: var(--shadow);
}

.scroll-guide {
    display: inline-flex;
    align-items: center;
    gap: 14px;
    margin-top: 76px;
    color: var(--subtext);
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.12em;
    text-transform: uppercase;
}

.scroll-line {
    display: inline-block;
    width: 62px;
    height: 1px;
    background: var(--border);
}

.section {
    padding: 130px 0;
}

.section-muted {
    background: var(--surface-muted);
}

.section-heading {
    display: grid;
    grid-template-columns: minmax(0, 1.25fr) minmax(280px, 0.75fr);
    gap: 48px;
    align-items: end;
    margin-bottom: 58px;
}

.section-heading h2 {
    margin: 0;
    font-size: clamp(2.6rem, 5vw, 4.6rem);
    line-height: 1.12;
    letter-spacing: -0.055em;

    /* 日本語の単語途中で不自然に改行されるのを防ぐ */
    word-break: keep-all;
    overflow-wrap: normal;
}

.section-introduction {
    margin: 0 0 8px;
    color: var(--subtext);
}

.series-card {
    min-height: 570px;
    overflow: hidden;
    display: grid;
    grid-template-columns: 1.08fr 0.92fr;
    border: 1px solid var(--border);
    border-radius: 38px;
    background: var(--surface);
    box-shadow: var(--shadow);
}

.series-content {
    display: flex;
    flex-direction: column;
    justify-content: center;
    padding: clamp(38px, 7vw, 78px);
}

.card-label {
    margin: 0 0 24px;
    color: var(--accent);
    font-size: 0.76rem;
    font-weight: 800;
    letter-spacing: 0.15em;
    text-transform: uppercase;
}

.series-content h3 {
    margin: 0;
    font-size: clamp(2.2rem, 5vw, 4.3rem);
    line-height: 1.1;
    letter-spacing: -0.055em;

    word-break: normal;
    overflow-wrap: anywhere;
}

.series-content > p:not(.card-label) {
    max-width: 620px;
    margin: 30px 0 0;
    color: var(--subtext);
}

.series-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 16px 28px;
    margin-top: 32px;
}

.text-link {
    display: inline-flex;
    align-items: center;
    gap: 12px;
    color: var(--accent);
    font-weight: 750;
}

.text-link span {
    transition: transform 0.2s ease;
}

.text-link:hover span {
    transform: translateX(4px);
}

.series-visual {
    position: relative;
    min-height: 480px;
    overflow: hidden;
    background:
        radial-gradient(
            circle at 70% 30%,
            rgba(115, 159, 255, 0.5),
            transparent 35%
        ),
        linear-gradient(145deg, #1644a8, #557ef2);
}

.visual-grid {
    position: absolute;
    inset: 0;
    opacity: 0.16;
    background-image:
        linear-gradient(rgba(255, 255, 255, 0.6) 1px, transparent 1px),
        linear-gradient(90deg, rgba(255, 255, 255, 0.6) 1px, transparent 1px);
    background-size: 42px 42px;
}

.visual-camera {
    position: absolute;
    top: 18%;
    left: 14%;
    width: 116px;
    height: 82px;
    border: 2px solid rgba(255, 255, 255, 0.8);
    border-radius: 18px;
    transform: rotate(-8deg);
}

.visual-camera::before {
    content: "";
    position: absolute;
    top: -20px;
    left: 24px;
    width: 52px;
    height: 22px;
    border: 2px solid rgba(255, 255, 255, 0.8);
    border-bottom: 0;
    border-radius: 10px 10px 0 0;
}

.camera-lens {
    position: absolute;
    top: 18px;
    left: 38px;
    width: 42px;
    height: 42px;
    border: 2px solid rgba(255, 255, 255, 0.9);
    border-radius: 50%;
}

.camera-lens::after {
    content: "";
    position: absolute;
    inset: 9px;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.85);
}

.visual-point {
    position: absolute;
    width: 14px;
    height: 14px;
    border: 3px solid rgba(255, 255, 255, 0.95);
    border-radius: 50%;
    background: #4d78e6;
    box-shadow: 0 0 0 8px rgba(255, 255, 255, 0.12);
}

.visual-point-one {
    right: 18%;
    bottom: 22%;
}

.visual-point-two {
    right: 39%;
    bottom: 12%;
}

.visual-point-three {
    right: 10%;
    bottom: 48%;
}

.visual-line {
    position: absolute;
    height: 2px;
    background: rgba(255, 255, 255, 0.65);
    transform-origin: left center;
}

.visual-line-one {
    top: 39%;
    left: 30%;
    width: 50%;
    transform: rotate(31deg);
}

.visual-line-two {
    top: 41%;
    left: 30%;
    width: 48%;
    transform: rotate(45deg);
}

.visual-line-three {
    top: 38%;
    left: 30%;
    width: 58%;
    transform: rotate(15deg);
}

.field-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 20px;
}

.field-card {
    min-height: 350px;
    padding: 38px;
    border: 1px solid var(--border);
    border-radius: 28px;
    background: var(--surface);
    transition:
        transform 0.25s ease,
        box-shadow 0.25s ease;
}

.field-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow);
}

.field-number {
    margin-bottom: 48px;
    color: var(--accent);
    font-size: 0.78rem;
    font-weight: 800;
    letter-spacing: 0.12em;
}

.field-card h3 {
    margin: 0;
    font-size: 1.65rem;
    letter-spacing: -0.035em;
}

.field-card p {
    margin: 18px 0 0;
    color: var(--subtext);
}

.field-card ul {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin: 26px 0 0;
    padding: 0;
    list-style: none;
}

.field-card li {
    padding: 6px 10px;
    border: 1px solid var(--border);
    border-radius: 999px;
    color: var(--subtext);
    font-size: 0.77rem;
    font-weight: 650;
}

.about-layout {
    display: grid;
    grid-template-columns: 0.75fr 1.25fr;
    gap: 110px;
}

.about-heading h2 {
    margin: 0;
    font-size: clamp(3rem, 7vw, 6rem);
    line-height: 1;
    letter-spacing: -0.07em;
}

.about-name {
    margin: 18px 0 0;
    color: var(--subtext);
    font-size: 0.94rem;
}

.about-content {
    max-width: 680px;
}

.about-content p {
    margin: 0 0 24px;
    color: var(--subtext);
}

.about-content .about-lead {
    color: var(--text);
    font-size: clamp(1.6rem, 3vw, 2.4rem);
    font-weight: 650;
    line-height: 1.45;
    letter-spacing: -0.035em;
}

.about-links {
    display: flex;
    flex-wrap: wrap;
    gap: 26px;
    margin-top: 34px;
}

.contact-section {
    padding: 30px 0 110px;
}

.contact-card {
    padding: clamp(42px, 8vw, 90px);
    border-radius: 38px;
    background:
        radial-gradient(
            circle at 85% 15%,
            rgba(255, 255, 255, 0.18),
            transparent 32%
        ),
        #172445;
    color: #ffffff;
}

.contact-card .section-label {
    color: #a9c3ff;
}

.contact-card h2 {
    max-width: 950px;
    margin: 0;
    font-size: clamp(2.6rem, 7vw, 5.6rem);
    line-height: 1.04;
    letter-spacing: -0.065em;
}

.contact-card p:not(.section-label) {
    max-width: 620px;
    margin: 30px 0 0;
    color: rgba(255, 255, 255, 0.72);
}

.button-light {
    margin-top: 38px;
    border-color: #ffffff;
    background: #ffffff;
    color: #172445;
}

.site-footer {
    padding: 48px 0;
    border-top: 1px solid var(--border);
}

.footer-inner {
    display: flex;
    justify-content: space-between;
    gap: 40px;
    color: var(--subtext);
    font-size: 0.86rem;
}

.footer-inner p {
    margin: 5px 0;
}

.footer-logo {
    color: var(--text);
    font-size: 1rem;
    font-weight: 800;
}

.footer-meta {
    text-align: right;
}

.footer-meta a:hover {
    color: var(--text);
}

@media (max-width: 900px) {
    .desktop-nav {
        display: none;
    }

    .menu-button {
        display: block;
    }

    .mobile-nav {
        position: fixed;
        inset: 0;
        z-index: 101;
        display: flex;
        visibility: hidden;
        flex-direction: column;
        justify-content: center;
        gap: 22px;
        padding: 80px 28px;
        background: var(--background);
        opacity: 0;
        transform: translateY(-10px);
        transition:
            opacity 0.25s ease,
            transform 0.25s ease,
            visibility 0.25s ease;
    }

    .mobile-nav.open {
        visibility: visible;
        opacity: 1;
        transform: translateY(0);
    }

    .mobile-nav a {
        font-size: 2rem;
        font-weight: 700;
        letter-spacing: -0.04em;
    }

    .section-heading,
    .series-card,
    .about-layout {
        grid-template-columns: 1fr;
    }

    .section-heading,
    .about-layout {
        gap: 44px;
    }

    .series-visual {
        min-height: 410px;
    }

    .section-heading {
        min-width: 0;
        width: 100%;
    }

    .section-heading > * {
        min-width: 0;
        max-width: 100%;
    }

    .section-heading h2 {
        max-width: 100%;
        font-size: clamp(2.2rem, 8vw, 3.2rem);
        line-height: 1.15;
        letter-spacing: -0.05em;
        word-break: normal;
        overflow-wrap: anywhere;
    }

    .section-introduction {
        max-width: 100%;
        overflow-wrap: anywhere;
    }


}

@media (max-width: 680px) {
    .container {
        width: min(calc(100% - 32px), var(--max-width));
    }

    .header-inner {
        min-height: 66px;
    }

    .hero {
        min-height: auto;
        padding: 140px 0 80px;
    }

    .hero h1 {
        font-size: clamp(2.5rem, 11.5vw, 3.6rem);
        line-height: 1;
        letter-spacing: -0.06em;
    }

    .hero-description {
        margin-top: 30px;
        line-height: 1.85;
    }

    .hero-actions {
        align-items: stretch;
        flex-direction: column;
    }

    .button {
        width: 100%;
    }

    .scroll-guide {
        margin-top: 52px;
    }

    .section {
        padding: 90px 0;
    }

    .section-heading {
        margin-bottom: 38px;
    }

    .series-card,
    .contact-card {
        border-radius: 26px;
    }

    .series-content {
        padding: 34px 26px 40px;
    }

    .series-content h3 {
        font-size: 2.1rem;
        word-break: normal;
        overflow-wrap: anywhere;
    }

    .series-visual {
        min-height: 330px;
    }

    .field-grid {
        grid-template-columns: 1fr;
    }

    .field-card {
        min-height: auto;
        padding: 30px;
    }

    .field-number {
        margin-bottom: 30px;
    }

    .about-layout {
        gap: 48px;
    }

    .contact-section {
        padding-bottom: 70px;
    }

    .contact-card {
        padding: 48px 27px;
    }

    .footer-inner {
        flex-direction: column;
    }

    .footer-meta {
        text-align: left;
    }

    .series-content {
        min-width: 0;
    }

    .section-heading {
        margin-bottom: 38px;
    }

}

@media (prefers-reduced-motion: reduce) {
    html {
        scroll-behavior: auto;
    }

    *,
    *::before,
    *::after {
        scroll-behavior: auto !important;
        transition-duration: 0.01ms !important;
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
    }
}

/* --------------------------------
   Articles page
-------------------------------- */

.articles-hero {
    position: relative;
    overflow: hidden;
    padding: 170px 0 100px;
}

.articles-hero::after {
    content: "";
    position: absolute;
    top: -220px;
    right: -180px;
    width: 600px;
    height: 600px;
    border-radius: 50%;
    background:
        radial-gradient(
            circle,
            rgba(57, 116, 255, 0.17),
            rgba(57, 116, 255, 0)
        );
    pointer-events: none;
}

.articles-hero-inner {
    position: relative;
    z-index: 1;
}

.articles-hero h1 {
    max-width: 920px;
    margin: 0;
    font-size: clamp(3.5rem, 9vw, 7.5rem);
    line-height: 1.02;
    letter-spacing: -0.07em;
    word-break: keep-all;
    overflow-wrap: normal;
}

.articles-hero-description {
    max-width: 760px;
    margin: 38px 0 0;
    color: var(--subtext);
    font-size: clamp(1rem, 2vw, 1.22rem);
    line-height: 2;
}

.article-summary {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-top: 34px;
}

.article-summary span {
    padding: 8px 14px;
    border: 1px solid var(--border);
    border-radius: 999px;
    background: var(--surface);
    color: var(--subtext);
    font-size: 0.8rem;
    font-weight: 700;
}

.articles-hero-actions {
    margin-top: 28px;
}

.articles-section {
    padding-top: 50px;
}

.article-category-nav {
    position: sticky;
    top: 90px;
    z-index: 20;
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 90px;
    padding: 14px;
    border: 1px solid var(--border);
    border-radius: 22px;
    background: var(--header-background);
    backdrop-filter: blur(20px);
}

.category-nav-link {
    padding: 9px 14px;
    border-radius: 999px;
    color: var(--subtext);
    font-size: 0.8rem;
    font-weight: 700;
    transition:
        color 0.2s ease,
        background-color 0.2s ease;
}

.category-nav-link:hover {
    background: var(--surface);
    color: var(--text);
}

.article-category {
    scroll-margin-top: 180px;
    padding-bottom: 120px;
}

.article-category-heading {
    display: grid;
    grid-template-columns: 70px minmax(0, 1fr);
    gap: 30px;
    margin-bottom: 42px;
}

.article-category-number {
    margin: 10px 0 0;
    color: var(--accent);
    font-size: 0.8rem;
    font-weight: 800;
    letter-spacing: 0.15em;
}

.article-category-english {
    margin: 0 0 10px;
    color: var(--accent);
    font-size: 0.75rem;
    font-weight: 800;
    letter-spacing: 0.12em;
    text-transform: uppercase;
}

.article-category-heading h2 {
    margin: 0;
    font-size: clamp(2rem, 5vw, 4.2rem);
    line-height: 1.1;
    letter-spacing: -0.055em;
    word-break: keep-all;
    overflow-wrap: normal;
}

.article-category-description {
    max-width: 700px;
    margin: 20px 0 0;
    color: var(--subtext);
}

.article-items {
    border-top: 1px solid var(--border);
}

.article-item {
    display: grid;
    grid-template-columns: 70px minmax(0, 1fr) 30px;
    gap: 30px;
    align-items: center;
    min-height: 96px;
    border-bottom: 1px solid var(--border);
    transition:
        padding 0.2s ease,
        color 0.2s ease,
        background-color 0.2s ease;
}

.article-item:hover {
    padding: 0 18px;
    background: var(--surface);
    color: var(--accent);
}

.article-number {
    color: var(--accent);
    font-size: 0.78rem;
    font-weight: 800;
    letter-spacing: 0.1em;
}

.article-title {
    font-size: clamp(1rem, 2vw, 1.2rem);
    font-weight: 650;
    line-height: 1.55;
}

.article-arrow {
    color: var(--subtext);
    font-size: 1.05rem;
    text-align: right;
    transition: transform 0.2s ease;
}

.article-item:hover .article-arrow {
    transform: translate(3px, -3px);
}

.article-loading {
    color: var(--subtext);
}

@media (max-width: 680px) {
    .articles-hero {
        padding: 130px 0 75px;
    }

    .articles-hero h1 {
        font-size: clamp(2.4rem, 11vw, 3.5rem);
        line-height: 1.05;
        letter-spacing: -0.06em;
        word-break: normal;
        overflow-wrap: anywhere;
    }

    .article-category-nav {
        top: 76px;
        margin-bottom: 65px;
        flex-wrap: nowrap;
        overflow-x: auto;
        border-radius: 18px;
    }

    .category-nav-link {
        flex: 0 0 auto;
    }

    .article-category {
        padding-bottom: 85px;
    }

    .article-category-heading {
        grid-template-columns: 1fr;
        gap: 10px;
    }

    .article-category-number {
        margin-top: 0;
    }

    .article-item {
        grid-template-columns: 42px minmax(0, 1fr) 20px;
        gap: 12px;
        min-height: 88px;
    }

    .article-item:hover {
        padding: 0 8px;
    }
}