:root {
      --paper: #f3f0e8;
      --paper-deep: #e7e2d7;
      --paper-light: #faf8f2;
      --ink: #252722;
      --muted: #5e605b;
      --faint: #62635b;
      --line: #c9c5ba;
      --accent: #b53822;
      --accent-dark: #7f291b;
      --max: 1180px;
      --gutter: clamp(1rem, 3.8vw, 3.75rem);
      --serif: "Yu Mincho", "Hiragino Mincho ProN", "BIZ UDPMincho", serif;
      --sans: "Yu Gothic", "Hiragino Kaku Gothic ProN", "Meiryo", system-ui, sans-serif;
    }
    * { box-sizing: border-box; }
    html { scroll-behavior: smooth; }
    body { margin: 0; background: var(--paper); color: var(--ink); font: 1rem/1.8 var(--sans); letter-spacing: .02em; }
    body::selection { background: var(--accent); color: var(--paper-light); }
    a { color: var(--accent-dark); text-underline-offset: .18em; }
    a:hover { color: var(--accent); }
    a:focus-visible, summary:focus-visible { outline: 3px solid var(--accent); outline-offset: 4px; }
    img, svg, video { display: block; max-width: 100%; }
    h1, h2, h3, p, figure, dl, dd { margin: 0; }
    h1, h2, h3 { font-family: var(--serif); font-weight: 600; text-wrap: balance; }
    .wrap { width: min(var(--max), calc(100% - (var(--gutter) * 2))); margin-inline: auto; }
    .skip-link { position: absolute; top: .75rem; left: -9999px; z-index: 20; padding: .65rem .9rem; background: var(--accent); color: var(--paper-light); }
    .skip-link:focus { left: .9rem; }

    .site-header { border-bottom: 1px solid var(--line); background: var(--paper); }
    .header-inner { display: flex; align-items: center; justify-content: space-between; gap: 1.5rem; min-height: 72px; padding-block: .7rem; }
    .brand { display: inline-flex; align-items: baseline; flex-wrap: wrap; gap: .35rem .75rem; min-height: 44px; color: var(--ink); text-decoration: none; line-height: 1.25; }
    .brand-ja { font: 1.05rem/1.25 var(--serif); letter-spacing: .08em; }
    .brand-en { color: var(--muted); font-size: .7rem; letter-spacing: .15em; text-transform: uppercase; }
    .nav-list { display: flex; flex-wrap: wrap; justify-content: flex-end; gap: .1rem .2rem; padding: 0; margin: 0; list-style: none; }
    .nav-list a { display: inline-flex; align-items: center; min-height: 44px; padding: .45rem .7rem; color: var(--muted); font-size: .82rem; text-decoration: none; white-space: nowrap; }
    .nav-list a:hover { color: var(--accent-dark); }

    .hero { padding: clamp(4.5rem, 10vw, 9.5rem) 0 clamp(4rem, 9vw, 8rem); border-bottom: 1px solid var(--line); }
    .hero-grid { display: grid; grid-template-columns: minmax(0, .82fr) minmax(320px, 1.18fr); gap: clamp(2.5rem, 8vw, 8rem); align-items: center; }
    .kicker { color: var(--accent-dark); font-size: .72rem; font-weight: 700; letter-spacing: .19em; text-transform: uppercase; }
    .hero h1 { margin-top: 1rem; font-size: clamp(3.25rem, 6.3vw, 5.8rem); line-height: 1.22; letter-spacing: -.07em; }
    .hero h1 span { display: block; color: var(--accent); }
    .hero-lede { max-width: 34rem; margin-top: 2rem; color: var(--muted); font-size: clamp(1rem, 1.4vw, 1.18rem); line-height: 1.95; }
    .hero-link { display: inline-flex; align-items: center; min-height: 44px; margin-top: 1.7rem; color: var(--accent-dark); font-weight: 700; text-decoration-thickness: 1px; }
    .hero-link::after { content: "↘"; margin-left: .55rem; font-size: 1.15em; }
    .hero-meta { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 0; margin-top: 3rem; border-top: 1px solid var(--line); }
    .hero-meta div { padding: .85rem .8rem .1rem 0; border-right: 1px solid var(--line); }
    .hero-meta div + div { padding-left: .8rem; }
    .hero-meta div:last-child { border-right: 0; }
    .hero-meta dt { color: var(--faint); font-size: .7rem; letter-spacing: .1em; text-transform: uppercase; }
    .hero-meta dd { margin-top: .2rem; font: .95rem/1.35 var(--serif); }

    .concept-figure { padding: clamp(1.1rem, 2.4vw, 1.8rem); border: 1px solid var(--ink); background: var(--paper-light); }
    .concept-figure svg { width: 100%; height: auto; }
    .concept-figure figcaption { display: flex; justify-content: space-between; gap: 1rem; padding-top: .85rem; margin-top: .95rem; border-top: 1px solid var(--line); color: var(--muted); font-size: .72rem; letter-spacing: .08em; }
    .concept-figure figcaption strong { color: var(--accent-dark); font-weight: 700; }
    .schematic-frame { fill: var(--paper); stroke: var(--ink); stroke-width: 1.5; }
    .schematic-frame-light { fill: var(--paper-deep); stroke: var(--line); stroke-width: 1.5; }
    .schematic-accent { fill: var(--accent); }
    .schematic-ink { fill: var(--ink); }
    .schematic-line { fill: none; stroke: var(--ink); stroke-width: 2; }
    .schematic-line-light { fill: none; stroke: var(--line); stroke-width: 1.5; }
    .schematic-arrow { fill: none; stroke: var(--accent); stroke-width: 3; }
    .schematic-label { fill: var(--muted); font: 700 15px var(--sans); letter-spacing: 1.6px; }
    .schematic-copy { fill: var(--ink); font: 600 21px var(--serif); }

    .section { padding: clamp(4.5rem, 9vw, 8rem) 0; }
    .section + .section { border-top: 1px solid var(--line); }
    .section-heading { display: grid; grid-template-columns: minmax(10rem, .36fr) minmax(0, 1fr); gap: clamp(1.5rem, 7vw, 7rem); align-items: start; margin-bottom: clamp(2.7rem, 5vw, 4.5rem); }
    .section-index { display: block; padding-top: .4rem; color: var(--accent-dark); font-size: .7rem; font-weight: 700; letter-spacing: .16em; text-transform: uppercase; }
    .section-heading h2 { max-width: 18ch; font-size: clamp(2.1rem, 5vw, 4.45rem); line-height: 1.08; letter-spacing: -.075em; }
    .section-heading p { max-width: 34rem; margin-top: 1.25rem; color: var(--muted); line-height: 1.9; }
    .about-grid { display: grid; grid-template-columns: minmax(0, 1fr) minmax(15rem, .68fr); gap: clamp(2.5rem, 9vw, 10rem); align-items: start; }
    .about-copy { max-width: 44rem; font-size: clamp(1.05rem, 1.8vw, 1.35rem); line-height: 1.95; }
    .about-aside { padding-top: .9rem; border-top: 3px solid var(--accent); color: var(--muted); font-size: .87rem; }
    .about-aside strong { display: block; margin-bottom: .35rem; color: var(--ink); font: 1.15rem var(--serif); }
    .about-source { display: inline-flex; align-items: center; min-height: 44px; margin-top: .85rem; font-size: .8rem; font-weight: 700; }

    .process-list { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); border-top: 1px solid var(--ink); border-bottom: 1px solid var(--ink); }
    .process-item { min-height: 18rem; padding: 1.5rem clamp(1rem, 2.8vw, 2rem) 1.7rem 0; }
    .process-item + .process-item { padding-left: clamp(1rem, 2.8vw, 2rem); border-left: 1px solid var(--line); }
    .process-number { color: var(--accent); font-size: .8rem; font-weight: 700; letter-spacing: .16em; }
    .process-item h3 { margin-top: 3.8rem; font-size: clamp(1.45rem, 2.2vw, 2rem); line-height: 1.2; }
    .process-item p { max-width: 18rem; margin-top: .8rem; color: var(--muted); font-size: .9rem; }
    .process-note { max-width: 48rem; margin-top: 1.4rem; color: var(--muted); font-size: .86rem; }
    .process-note strong { color: var(--ink); }

    .samples { background: var(--paper-deep); }
    .sample-status { display: grid; grid-template-columns: auto minmax(0, 1fr); gap: 1rem; align-items: start; max-width: 44rem; padding-top: 1.4rem; border-top: 1px solid var(--ink); }
    .sample-mark { width: 1rem; height: 1rem; margin-top: .45rem; background: var(--accent); }
    .sample-status strong { display: block; font: 1.4rem var(--serif); }
    .sample-status p { color: var(--muted); }
    .sample-status small { display: block; margin-top: .55rem; color: var(--faint); font-size: .77rem; }

    .sources-intro { max-width: 47rem; margin-bottom: 2.1rem; color: var(--muted); }
    .source-list { border-top: 1px solid var(--ink); border-bottom: 1px solid var(--ink); }
    details + details { border-top: 1px solid var(--line); }
    summary { display: flex; align-items: center; justify-content: space-between; gap: 1rem; min-height: 64px; padding: .8rem 0; color: var(--ink); cursor: pointer; font: 600 clamp(1.05rem, 1.8vw, 1.35rem) var(--serif); list-style: none; }
    summary::-webkit-details-marker { display: none; }
    summary::after { content: "+"; flex: 0 0 auto; color: var(--accent); font: 1.5rem var(--sans); }
    details[open] summary::after { content: "−"; }
    .detail-body { max-width: 52rem; padding: 0 2.5rem 1.5rem 0; color: var(--muted); font-size: .88rem; }
    .detail-body p { margin-bottom: 1rem; }
    .source-label { display: inline-block; margin-right: .55rem; color: var(--accent-dark); font-size: .7rem; font-weight: 700; letter-spacing: .12em; text-transform: uppercase; }
    .source-links { display: flex; flex-wrap: wrap; gap: .25rem 1.25rem; }
    .source-links a { display: inline-flex; align-items: center; min-height: 44px; font-size: .8rem; font-weight: 700; }
    .sources-note { max-width: 52rem; margin-top: 1.4rem; color: var(--faint); font-size: .78rem; }

    .site-qr { display: grid; grid-template-columns: minmax(0, 1fr) 222px; gap: clamp(2rem, 8vw, 7rem); align-items: start; max-width: 58rem; padding: 1.35rem 0 2rem; margin-bottom: clamp(3rem, 6vw, 5rem); border-top: 1px solid var(--ink); border-bottom: 1px solid var(--line); }
    .site-qr-copy { max-width: 36rem; }
    .site-qr h3 { font-size: clamp(1.65rem, 3vw, 2.35rem); line-height: 1.25; }
    .site-qr p { max-width: 31rem; margin-top: .9rem; color: var(--muted); }
    .site-qr-url { display: inline-flex; align-items: center; min-height: 44px; margin-top: .85rem; font-weight: 700; overflow-wrap: anywhere; }
    .site-qr-downloads { display: flex; flex-wrap: wrap; gap: .25rem 1.25rem; margin-top: .35rem; }
    .site-qr-downloads a { display: inline-flex; align-items: center; min-height: 44px; font-size: .8rem; font-weight: 700; }
    .site-qr-figure { width: 222px; }
    .site-qr-figure img { width: 222px; height: 222px; background: #fff; image-rendering: pixelated; }
    .site-qr-figure figcaption { margin-top: .65rem; color: var(--faint); font-size: .75rem; }
    .activity-list { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 2rem; }
    .activity-item { border-top: 1px solid var(--ink); padding-top: 1.25rem; }
    .activity-item h3 { font-size: 1.75rem; }
    .activity-item img { width: 222px; height: 222px; margin-block: 1.25rem; }
    .activity-item a { display: inline-flex; align-items: center; min-height: 44px; overflow-wrap: anywhere; }
    .activity-item p { color: var(--muted); font-size: .85rem; }
    @media (max-width: 760px) { .activity-list { grid-template-columns: 1fr; } }
    footer { padding: 2.3rem 0 3rem; border-top: 1px solid var(--line); color: var(--muted); font-size: .75rem; }
    .footer-inner { display: flex; justify-content: space-between; gap: 1.5rem; }
    .footer-inner span:last-child { text-align: right; }
    @media (max-width: 880px) {
      .header-inner { align-items: flex-start; flex-direction: column; justify-content: center; }
      .nav-list { justify-content: flex-start; margin-left: -.7rem; }
      .hero-grid { grid-template-columns: 1fr; gap: 3.5rem; }
      .hero h1 { max-width: none; }
      .concept-figure { max-width: 46rem; }
      .section-heading { grid-template-columns: minmax(7rem, .28fr) minmax(0, 1fr); gap: 2rem; }
    }
    @media (max-width: 620px) {
      :root { --gutter: 1rem; }
      .header-inner { min-height: 0; padding-block: .8rem; }
      .brand { gap: .25rem .6rem; }
      .nav-list { display: grid; grid-template-columns: repeat(2, minmax(0, max-content)); width: 100%; margin: .25rem 0 -.35rem -.7rem; }
      .hero { padding-top: 4rem; }
      .hero h1 { font-size: clamp(3rem, 16vw, 5.2rem); }
      .hero-lede { margin-top: 1.4rem; font-size: 1rem; }
      .hero-meta { margin-top: 2.2rem; }
      .hero-meta div { padding-right: .45rem; }
      .hero-meta div + div { padding-left: .45rem; }
      .hero-meta dd { font-size: .84rem; }
      .concept-figure { padding: .75rem; }
      .concept-figure figcaption { display: block; }
      .concept-figure figcaption strong { display: block; margin-bottom: .35rem; }
      .section-heading { display: block; }
      .section-heading h2 { margin-top: .8rem; font-size: clamp(2.15rem, 12vw, 3.4rem); }
      .section-heading p { margin-top: 1rem; }
      .about-grid { grid-template-columns: 1fr; gap: 2.3rem; }
      .about-copy { font-size: 1.05rem; }
      .process-list { display: block; }
      .process-item { min-height: 0; padding: 1.25rem 0 1.5rem; }
      .process-item + .process-item { padding-left: 0; border-top: 1px solid var(--line); border-left: 0; }
      .process-item h3 { margin-top: 1.6rem; }
      .detail-body { padding-right: 0; }
      .detail-body, .process-item p, .process-note, .about-aside { font-size: 1rem; }
      .site-qr { grid-template-columns: 1fr; gap: 1.5rem; }
      .site-qr-figure { justify-self: start; }
      .footer-inner { display: block; }
      .footer-inner span { display: block; }
      .footer-inner span + span { margin-top: .5rem; }
      .footer-inner span:last-child { text-align: left; }
    }
    @media (prefers-reduced-motion: reduce) {
      html { scroll-behavior: auto; }
      *, *::before, *::after { animation-duration: .01ms !important; animation-iteration-count: 1 !important; transition-duration: .01ms !important; }
    }