:root {
  color-scheme: light dark;
  --canvas: #eef1ec;
  --surface: #e3e8e1;
  --surface-strong: #d6ded5;
  --text: #17201a;
  --muted: #506056;
  --line: #bcc8be;
  --accent: #2f6b4f;
  --accent-strong: #24563f;
  --on-accent: #f2f6f2;
  --radius: 14px;
  --content: 1160px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --canvas: #111713;
    --surface: #18211b;
    --surface-strong: #202c24;
    --text: #e7eee8;
    --muted: #a8b5ac;
    --line: #34443a;
    --accent: #75b18d;
    --accent-strong: #8dc5a2;
    --on-accent: #102017;
  }
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--canvas);
  color: var(--text);
  font-family: "Yu Gothic UI", "Hiragino Sans", "Noto Sans JP", system-ui, sans-serif;
  font-size: 16px;
  line-height: 1.85;
  text-rendering: optimizeLegibility;
}

a {
  color: inherit;
}

main {
  width: min(100% - 40px, var(--content));
  margin-inline: auto;
  padding: 72px 0 44px;
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 0.84fr) minmax(420px, 1.16fr);
  align-items: center;
  gap: clamp(44px, 7vw, 96px);
  min-height: min(720px, calc(100dvh - 40px));
}

.hero-copy {
  max-width: 580px;
}

.kicker {
  margin: 0 0 18px;
  color: var(--accent-strong);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

h1,
h2,
h3,
p {
  text-wrap: pretty;
}

h1 {
  max-width: 11ch;
  margin: 0;
  font-size: clamp(2.85rem, 6vw, 5.8rem);
  font-weight: 650;
  letter-spacing: -0.055em;
  line-height: 1.04;
}

.lead {
  max-width: 37rem;
  margin: 30px 0 0;
  color: var(--muted);
  font-size: clamp(1.03rem, 1.55vw, 1.18rem);
}

.source-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  margin-top: 30px;
  padding: 11px 18px;
  border: 1px solid var(--accent);
  border-radius: var(--radius);
  background: var(--accent);
  color: var(--on-accent);
  font-weight: 700;
  line-height: 1.35;
  text-decoration: none;
  transition: background-color 160ms ease, transform 160ms ease;
}

.source-link:hover {
  background: var(--accent-strong);
}

.source-link:active {
  transform: translateY(1px);
}

.source-link:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 4px;
}

.video-shell {
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  box-shadow: 0 28px 70px rgb(31 52 39 / 14%);
  aspect-ratio: 16 / 9;
}

.video-shell iframe {
  display: block;
  width: 100%;
  height: 100%;
  border: 0;
}

.reading-guide {
  padding: 88px 0 52px;
}

.section-heading {
  max-width: 680px;
  margin-bottom: 48px;
}

.section-heading h2,
.source-note h2 {
  margin: 0;
  font-size: clamp(1.85rem, 3vw, 2.7rem);
  letter-spacing: -0.035em;
  line-height: 1.2;
}

.section-heading p {
  margin: 12px 0 0;
  color: var(--muted);
}

.timeline {
  display: grid;
  gap: 0;
  margin: 0;
  padding: 0;
  list-style: none;
}

.timeline li {
  display: grid;
  grid-template-columns: 160px minmax(0, 720px);
  gap: clamp(30px, 7vw, 90px);
  padding: 34px 0 38px;
  border-top: 1px solid var(--line);
}

.timeline time {
  color: var(--accent-strong);
  font-family: ui-monospace, "Cascadia Mono", "SFMono-Regular", Consolas, monospace;
  font-size: 0.86rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  white-space: nowrap;
}

.timeline h3 {
  margin: -7px 0 8px;
  font-size: clamp(1.22rem, 2vw, 1.52rem);
  letter-spacing: -0.025em;
  line-height: 1.45;
}

.timeline p {
  max-width: 66ch;
  margin: 0;
  color: var(--muted);
}

.source-note {
  max-width: 860px;
  margin: 58px 0 86px auto;
  padding: clamp(26px, 5vw, 50px);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
}

.source-note p {
  margin: 18px 0 0;
  color: var(--muted);
}

.source-note ul {
  display: grid;
  gap: 8px;
  margin: 20px 0 0;
  padding-left: 1.25em;
  color: var(--muted);
}

footer {
  padding-top: 24px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 0.82rem;
}

footer p {
  margin: 0;
}

@media (max-width: 860px) {
  main {
    width: min(100% - 32px, var(--content));
    padding-top: 42px;
  }

  .hero {
    grid-template-columns: 1fr;
    gap: 38px;
    min-height: 0;
  }

  .hero-copy {
    max-width: 680px;
  }

  h1 {
    max-width: 12ch;
  }

  .video-shell {
    width: 100%;
  }

  .reading-guide {
    padding-top: 82px;
  }
}

@media (max-width: 560px) {
  main {
    width: min(100% - 28px, var(--content));
    padding: 28px 0 34px;
  }

  .kicker {
    margin-bottom: 14px;
  }

  h1 {
    font-size: clamp(2.55rem, 14vw, 4rem);
  }

  .lead {
    margin-top: 22px;
    font-size: 1rem;
  }

  .source-link {
    width: 100%;
    margin-top: 24px;
  }

  .reading-guide {
    padding: 72px 0 36px;
  }

  .section-heading {
    margin-bottom: 28px;
  }

  .timeline li {
    grid-template-columns: 1fr;
    gap: 10px;
    padding: 28px 0 31px;
  }

  .timeline h3 {
    margin-top: 0;
  }

  .source-note {
    margin: 44px 0 64px;
    padding: 24px;
  }

}

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

  .source-link {
    transition: none;
  }
}