:root {
  --bg: #0d1014;
  --bg-soft: #151a20;
  --paper: #ece9e2;
  --text: #e8eaed;
  --text-dark: #1f2429;
  --muted: #aeb5bd;
  --line: rgba(255,255,255,.14);
  --accent: #c4a86a;
  --max: 780px;
  --serif: "Yu Mincho", "Hiragino Mincho ProN", "Noto Serif JP", serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "Hiragino Kaku Gothic ProN", "Yu Gothic", sans-serif;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: var(--bg); color: var(--text); font-family: var(--sans); line-height: 2; letter-spacing: .025em; }
a { color: inherit; }
img { max-width: 100%; height: auto; }
button, audio { font: inherit; }
.skip-link { position: fixed; left: 1rem; top: -4rem; z-index: 1000; background: #fff; color: #111; padding: .6rem 1rem; }
.skip-link:focus { top: 1rem; }
.hero { min-height: 100svh; position: relative; display: grid; place-items: center; text-align: center; overflow: hidden; background: radial-gradient(circle at 50% 25%, #273443 0, #121820 36%, #090c10 75%); }
.hero::before { content: ""; position: absolute; inset: 0; opacity: .16; background-image: linear-gradient(rgba(255,255,255,.03) 1px, transparent 1px), linear-gradient(90deg, rgba(255,255,255,.03) 1px, transparent 1px); background-size: 44px 44px; }
.hero__shade { position: absolute; inset: 0; background: linear-gradient(180deg, transparent 50%, var(--bg)); }
.hero__content { position: relative; z-index: 1; padding: 3rem 1.5rem; }
.eyebrow, .section-no, .audio-card__label { margin: 0 0 .75rem; color: var(--accent); font-size: .72rem; letter-spacing: .25em; font-weight: 700; }
h1, h2, h3 { font-family: var(--serif); font-weight: 600; }
h1 { margin: 0; font-size: clamp(2.45rem, 8vw, 5.3rem); letter-spacing: .08em; line-height: 1.3; }
.subtitle { margin: 1rem 0 0; color: #d7dbe0; font-family: var(--serif); font-size: clamp(1rem, 3vw, 1.35rem); }
.tagline { margin: 3rem 0 0; color: var(--muted); }
.scroll-cue { display: inline-flex; gap: .8rem; margin-top: 3rem; text-decoration: none; font-size: .72rem; letter-spacing: .2em; color: var(--muted); }
.toc { position: sticky; top: 0; z-index: 50; border-bottom: 1px solid var(--line); background: rgba(13,16,20,.93); backdrop-filter: blur(12px); }
.toc__toggle { display: none; width: 100%; padding: .8rem 1rem; color: var(--text); background: transparent; border: 0; text-align: left; }
.toc__lists { max-width: 1100px; margin: 0 auto; padding: .7rem 1rem; }
.toc ol { margin: 0; padding: 0; display: flex; align-items: center; justify-content: center; gap: .75rem 1.1rem; flex-wrap: wrap; list-style: none; }
.toc__supplement { margin-top: .5rem !important; padding-top: .5rem !important; border-top: 1px solid rgba(255,255,255,.08); }
.toc a { color: var(--muted); text-decoration: none; font-size: .76rem; }
.toc__main a { white-space: nowrap; }
.toc-item--supplement { display: inline-flex; align-items: center; gap: .55rem; white-space: nowrap; }
.toc-number--appendix { font-weight: 700; color: #d4af37; }
.toc-title { color: var(--muted); }
.toc a:hover, .toc a:focus, .toc a:hover .toc-title, .toc a:focus .toc-title { color: #fff; }
.section { padding: clamp(5rem, 10vw, 9rem) 1.35rem; border-bottom: 1px solid var(--line); }
.section__inner { width: min(100%, var(--max)); margin: 0 auto; }
.section h2 { margin: .2rem 0 2.4rem; font-size: clamp(1.85rem, 5vw, 3rem); line-height: 1.45; letter-spacing: .06em; }
.section p { margin: 0 0 1.6rem; }
.opening { font-family: var(--serif); font-size: clamp(1.22rem, 3.4vw, 1.7rem); line-height: 2; }
.epigraph { padding-left: 1.2rem; border-left: 2px solid var(--accent); color: var(--muted); font-family: var(--serif); font-size: 1.08rem; }
.section--dark { background: #090c10; }
.section--paper { background: var(--paper); color: var(--text-dark); }
.section--paper .section-no { color: #816d40; }
.notice { margin-top: 3rem; padding: 1.5rem; border: 1px solid var(--line); background: rgba(255,255,255,.035); }
.notice h3 { margin-top: 0; }
blockquote { margin: 3rem 0; padding: 2rem clamp(1.2rem, 5vw, 3rem); border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); font-family: var(--serif); font-size: 1.18rem; text-align: center; }
blockquote p { margin: 0 !important; }
.audio-card { margin: 3rem 0; padding: clamp(1.2rem, 4vw, 2rem); border: 1px solid var(--line); border-radius: 14px; background: var(--bg-soft); }
.audio-card__head { display: flex; gap: 1rem; align-items: center; margin-bottom: 1.2rem; }
.audio-card__head h3, .audio-card__label { margin: 0; }
.audio-card__icon { display: grid; place-items: center; width: 46px; aspect-ratio: 1; border: 1px solid var(--accent); border-radius: 50%; color: var(--accent); }
audio { width: 100%; }
.caption, figcaption { color: var(--muted); font-size: .78rem; line-height: 1.7; }
.gallery { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1.2rem; margin: 3rem 0; }
.gallery figure { margin: 0; }
.image-button { width: 100%; padding: 0; border: 1px solid var(--line); background: #080a0d; cursor: zoom-in; overflow: hidden; }
.image-button img { display: block; width: 100%; aspect-ratio: 3/5; object-fit: cover; object-position: top; transition: transform .35s ease; }
.image-button:hover img { transform: scale(1.025); }
.questions { margin: 3.2rem 0; padding: 2.2rem 0; border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.questions p { margin: .55rem 0; font-family: var(--serif); font-size: clamp(1.15rem, 3.2vw, 1.55rem); }
.epilogue { background: radial-gradient(circle at 50% 20%, #1b252f, var(--bg) 65%); }
.closing { margin-top: 4rem !important; font-family: var(--serif); font-size: clamp(1.25rem, 3.8vw, 1.8rem); text-align: center; }
.legal-note { padding: 3rem 1.35rem; background: #080a0d; color: var(--muted); font-size: .82rem; }
.legal-note h2 { color: var(--text); font-size: 1rem; }
footer { padding: 2rem 1.2rem; display: flex; justify-content: center; gap: 2rem; color: var(--muted); font-size: .75rem; }
.modal { width: min(94vw, 920px); max-height: 92vh; padding: 0; border: 1px solid var(--line); background: #050607; }
.modal::backdrop { background: rgba(0,0,0,.88); }
.modal img { display: block; max-height: 88vh; margin: auto; }
.modal__close { position: fixed; right: 1.4rem; top: 1rem; z-index: 2; width: 44px; height: 44px; border: 1px solid rgba(255,255,255,.45); border-radius: 50%; background: rgba(0,0,0,.65); color: white; cursor: pointer; font-size: 1.6rem; }
.reveal { opacity: 0; transform: translateY(24px); transition: opacity .85s ease, transform .85s ease; }
.reveal.is-visible { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } .reveal { opacity: 1; transform: none; transition: none; } .image-button img { transition: none; } }
@media (max-width: 760px) {
  .toc__toggle { display: block; }
  .toc__lists { display: none; padding-top: 0; }
  .toc.is-open .toc__lists { display: block; }
  .toc ol { flex-direction: column; align-items: stretch; gap: .2rem; }
  .toc__supplement { margin-top: .35rem !important; padding-top: .35rem !important; }
  .toc a { display: block; padding: .45rem 0; }
  .toc-item--supplement { display: flex; white-space: normal; }
  .gallery { grid-template-columns: 1fr; }
  .image-button img { aspect-ratio: 4/5; }
  footer { flex-direction: column; align-items: center; gap: .2rem; }
}


/* Version 1.1: supplemental music-collaboration chapter */
.section--supplement {
  background:
    linear-gradient(180deg, rgba(196,168,106,.055), transparent 24%),
    #11151a;
}
.section--supplement .section-no { color: #d2b875; }
.evidence { margin: 3rem 0; }
.evidence figure, .gallery--evidence figure { margin: 0; }
.gallery--evidence {
  grid-template-columns: minmax(0, .72fr) minmax(0, 1.28fr);
  align-items: start;
}
.image-button--natural img {
  width: 100%;
  height: auto;
  aspect-ratio: auto;
  object-fit: contain;
  object-position: center;
  background: #080a0d;
}
.notice--source {
  border-color: rgba(196,168,106,.35);
  background: rgba(196,168,106,.055);
}
@media (max-width: 760px) {
  .gallery--evidence { grid-template-columns: 1fr; }
}


/* Screen-reader-only text: remains available to assistive technology. */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}