:root {
  --bg: #07111f;
  --bg-soft: #0c1728;
  --panel: #101d31;
  --panel-2: #13243b;
  --text: #edf3fb;
  --muted: #9fb0c5;
  --line: rgba(255,255,255,.10);
  --accent: #67d3ff;
  --accent-2: #8cf0c7;
  --shadow: 0 20px 60px rgba(0,0,0,.28);
  --radius: 22px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background:
    radial-gradient(circle at 18% 0%, rgba(80, 144, 255, .16), transparent 32rem),
    radial-gradient(circle at 86% 14%, rgba(71, 228, 187, .10), transparent 28rem),
    var(--bg);
  color: var(--text);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans JP", sans-serif;
  line-height: 1.75;
}

a { color: inherit; text-decoration: none; }
.container { width: min(1160px, calc(100% - 40px)); margin: 0 auto; }
.narrow { width: min(850px, 100%); }

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(18px);
  background: rgba(7, 17, 31, .82);
  border-bottom: 1px solid rgba(103, 211, 255, .16);
  box-shadow: 0 10px 32px rgba(0, 0, 0, .16);
}
.header-inner {
  min-height: 78px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}
.brand {
  flex: 0 0 auto;
  font-weight: 800;
  letter-spacing: .02em;
}
nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 8px;
  padding: 10px 0;
}
nav a {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 36px;
  padding: 7px 11px;
  color: #b7c6d9;
  font-size: .78rem;
  font-weight: 700;
  line-height: 1.2;
  white-space: nowrap;
  border: 1px solid rgba(255,255,255,.10);
  border-radius: 11px;
  background: linear-gradient(180deg, rgba(255,255,255,.055), rgba(255,255,255,.022));
  box-shadow: inset 0 1px 0 rgba(255,255,255,.025);
  transition: color .18s ease, background .18s ease, border-color .18s ease, transform .18s ease, box-shadow .18s ease;
}
nav a:hover {
  color: var(--text);
  border-color: rgba(103,211,255,.42);
  background: linear-gradient(180deg, rgba(103,211,255,.13), rgba(103,211,255,.045));
  transform: translateY(-1px);
  box-shadow: 0 8px 20px rgba(0,0,0,.18), inset 0 1px 0 rgba(255,255,255,.05);
}
nav a:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}
nav a[href="license.html"],
nav a[href="#license-v11"],
nav a[href="#fee-policy"] {
  border-color: rgba(140,240,199,.25);
  background: linear-gradient(180deg, rgba(140,240,199,.09), rgba(103,211,255,.035));
}
.footer-links a { color: var(--muted); font-size: .88rem; }
.footer-links a:hover { color: var(--text); }

.hero { padding: 96px 0 86px; }
.hero-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.25fr) minmax(320px, .75fr);
  gap: 64px;
  align-items: center;
}
.eyebrow {
  margin: 0 0 12px;
  color: var(--accent);
  font-size: .78rem;
  font-weight: 800;
  letter-spacing: .14em;
  text-transform: uppercase;
}
h1, h2, h3 { margin-top: 0; line-height: 1.18; }
h1 {
  margin-bottom: 18px;
  font-size: clamp(3rem, 7vw, 6.5rem);
  letter-spacing: -.055em;
}
h2 {
  margin-bottom: 18px;
  font-size: clamp(2rem, 4vw, 3.6rem);
  letter-spacing: -.035em;
}
h3 { font-size: 1.18rem; }
.hero-title-en {
  margin: -2px 0 24px;
  color: var(--muted);
  font-size: clamp(1.2rem, 2.2vw, 2rem);
  font-weight: 650;
  line-height: 1.35;
  letter-spacing: -.02em;
}
.heading-en {
  margin: -8px 0 22px;
  color: var(--muted);
  font-size: clamp(1.02rem, 1.8vw, 1.35rem);
  font-weight: 600;
  line-height: 1.45;
}
.lang-en {
  color: var(--muted);
  font-size: .92em;
}
.lead, .section-intro {
  color: #c7d4e4;
  font-size: clamp(1.05rem, 1.6vw, 1.3rem);
}
.lead { max-width: 760px; margin-bottom: 0; }
.lead.lang-en { margin-top: 12px; }
.section-intro { max-width: 920px; }
.section-intro.lang-en { margin-top: 12px; }

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 30px;
}
.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  padding: 0 20px;
  border-radius: 999px;
  border: 1px solid var(--line);
  font-weight: 750;
  transition: transform .18s ease, background .18s ease, border-color .18s ease;
}
.button:hover { transform: translateY(-2px); }
.button.primary {
  color: #03121c;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  border-color: transparent;
}
.button.secondary { background: rgba(255,255,255,.045); }

.flow-card {
  padding: 28px;
  background: linear-gradient(180deg, rgba(18, 34, 57, .96), rgba(12, 23, 40, .95));
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}
.flow-node {
  display: grid;
  grid-template-columns: 42px 1fr;
  gap: 4px 12px;
  align-items: center;
  padding: 14px 16px;
  background: rgba(255,255,255,.035);
  border: 1px solid rgba(255,255,255,.065);
  border-radius: 15px;
}
.flow-node span {
  grid-row: span 2;
  color: var(--accent);
  font-weight: 800;
  font-size: .82rem;
}
.flow-node strong { font-size: 1.03rem; }
.flow-node small { color: var(--muted); }
.flow-arrow { text-align: center; color: #536a86; padding: 4px 0; }

.section { padding: 88px 0; }
.section.alt {
  background: rgba(255,255,255,.025);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}
.section.compact { padding: 62px 0; }

.feature-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
  margin-top: 38px;
}
.card {
  min-height: 250px;
  padding: 25px;
  background: linear-gradient(180deg, rgba(18,34,57,.92), rgba(11,23,39,.92));
  border: 1px solid var(--line);
  border-radius: 18px;
}
.card p { color: var(--muted); }
.card p.lang-en { margin-top: 10px; font-size: .86rem; line-height: 1.65; }
.card-kicker {
  margin: 0 0 24px;
  color: var(--accent) !important;
  font-size: .8rem;
  font-weight: 800;
  letter-spacing: .12em;
}

.why-stack-section { border-top: 1px solid var(--line); }
.stack-overview {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 24px;
  margin-top: 38px;
  align-items: stretch;
}
.stack-figure-wide {
  width: min(100%, 960px);
  margin-inline: auto;
}
.stack-figure {
  margin: 0;
  overflow: hidden;
  background: linear-gradient(180deg, rgba(18,34,57,.92), rgba(11,23,39,.92));
  border: 1px solid var(--line);
  border-radius: 18px;
}
.stack-figure img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: contain;
}
.stack-figure figcaption {
  padding: 13px 16px 15px;
  color: var(--muted);
  font-size: .78rem;
  line-height: 1.55;
  border-top: 1px solid var(--line);
}
.stack-figure figcaption span { display: block; margin-top: 4px; }
.stack-concept-flow {
  display: grid;
  align-content: center;
  gap: 7px;
  width: min(100%, 960px);
  margin-inline: auto;
  padding: 24px;
  background: linear-gradient(180deg, rgba(18,34,57,.96), rgba(12,23,40,.95));
  border: 1px solid var(--line);
  border-radius: 18px;
  box-shadow: var(--shadow);
}
.stack-node {
  display: grid;
  grid-template-columns: minmax(110px, .45fr) 1fr;
  gap: 18px;
  align-items: center;
  padding: 14px 17px;
  background: rgba(255,255,255,.035);
  border: 1px solid rgba(255,255,255,.065);
  border-radius: 14px;
}
.stack-node strong { color: var(--accent); }
.stack-node span { color: #c7d4e4; font-size: .88rem; }
.stack-node-output strong { color: var(--accent-2); }
.stack-arrow { color: #637b99; text-align: center; line-height: 1; }
.why-stack-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
  margin-top: 24px;
}
.why-stack-card { min-height: 0; }
.why-stack-card .card-kicker { margin-top: 24px; margin-bottom: 12px; }
.stack-card-figure img {
  aspect-ratio: 1 / 1;
  object-fit: contain;
}
.stack-card-figure figcaption { text-align: center; }
.physical-path {
  display: flex;
  flex-wrap: wrap;
  gap: 7px;
  align-items: center;
  margin: 18px 0;
  padding: 13px;
  color: #c7d4e4;
  font-size: .76rem;
  background: rgba(255,255,255,.035);
  border: 1px solid var(--line);
  border-radius: 12px;
}
.physical-path b { color: var(--accent); font-weight: 700; }
.stack-closing {
  margin-top: 24px;
  padding: 24px 26px;
  background: linear-gradient(135deg, rgba(103,211,255,.08), rgba(140,240,199,.055));
  border: 1px solid var(--line);
  border-radius: 18px;
}
.stack-closing p { margin: 0; }
.stack-closing p + p { margin-top: 10px; }

.architecture {
  display: flex;
  gap: 9px;
  align-items: stretch;
  overflow-x: auto;
  padding: 26px 0 6px;
}
.arch-item {
  min-width: 165px;
  padding: 18px 16px;
  border: 1px solid var(--line);
  border-radius: 15px;
  background: var(--panel);
}
.arch-item strong, .arch-item span { display: block; }
.arch-item span { margin-top: 8px; color: var(--muted); font-size: .82rem; }
.arch-arrow { display: grid; place-items: center; color: #637b99; }

.layer-map {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(260px, .7fr);
  gap: 30px;
  margin: 38px 0 34px;
  align-items: stretch;
}
.layer-stack {
  display: grid;
  gap: 8px;
  padding: 22px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: linear-gradient(180deg, rgba(18,34,57,.92), rgba(10,21,36,.94));
  box-shadow: var(--shadow);
}
.layer-row {
  display: grid;
  grid-template-columns: 44px minmax(0, 1fr) minmax(180px, .75fr);
  gap: 14px;
  align-items: center;
  padding: 14px 16px;
  border: 1px solid rgba(255,255,255,.07);
  border-radius: 14px;
  background: rgba(255,255,255,.035);
}
.layer-row .layer-num {
  color: var(--accent);
  font-size: .78rem;
  font-weight: 800;
  letter-spacing: .08em;
}
.layer-row strong { font-size: 1rem; }
.layer-row small { color: var(--muted); line-height: 1.45; }
.layer-arrow {
  text-align: center;
  color: #536a86;
  line-height: 1;
}
.layer-note {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  padding: 26px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: rgba(255,255,255,.03);
}
.layer-note p { color: var(--muted); }
.layer-note strong { color: var(--text); }
.layer-axis {
  display: grid;
  gap: 10px;
  margin-top: 18px;
}
.layer-axis div {
  padding: 12px 14px;
  border-left: 2px solid var(--accent);
  background: rgba(255,255,255,.025);
}
.layer-axis span {
  display: block;
  color: var(--muted);
  font-size: .82rem;
}
.flow-label {
  margin: 34px 0 0;
  color: var(--accent-2);
  font-size: .76rem;
  font-weight: 800;
  letter-spacing: .13em;
  text-transform: uppercase;
}

.split-panel {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 52px;
  align-items: start;
}
.split-panel > div > p.lang-en { margin-top: 10px; }
.build-list {
  display: grid;
  gap: 12px;
}
.build-list > div {
  display: grid;
  grid-template-columns: 50px 1fr;
  gap: 14px;
  padding: 17px;
  border: 1px solid var(--line);
  border-radius: 15px;
  background: rgba(255,255,255,.035);
}
.build-list span { color: var(--accent); font-weight: 800; }
.build-list p { margin: 0; color: var(--muted); }
.build-list strong { color: var(--text); }
.build-list .lang-en { color: var(--muted); font-weight: 500; }

.callout {
  display: flex;
  justify-content: space-between;
  gap: 36px;
  align-items: center;
  padding: 34px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: linear-gradient(135deg, rgba(26, 55, 89, .78), rgba(15, 40, 52, .78));
}
.callout h2 { margin-bottom: 10px; }
.callout p { margin-bottom: 0; color: #c5d3e4; }
.callout p.lang-en { margin-top: 10px; color: var(--muted); }

.site-footer {
  padding: 28px 0 36px;
  border-top: 1px solid var(--line);
  color: var(--muted);
}
.footer-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 20px;
}
.footer-links { display: flex; gap: 18px; }

@media (max-width: 1050px) {
  .header-inner { gap: 16px; }
  nav { gap: 6px; }
  nav a {
    padding: 6px 9px;
    font-size: .72rem;
  }
}

@media (max-width: 900px) {
  .hero-grid, .split-panel, .layer-map, .stack-overview { grid-template-columns: 1fr; }
  .feature-grid, .why-stack-grid { grid-template-columns: repeat(2, 1fr); }
  .hero { padding-top: 70px; }
  .header-inner {
    min-height: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 8px;
    padding: 10px 0 12px;
  }
  .brand { padding-left: 2px; }
  nav {
    flex-wrap: nowrap;
    justify-content: flex-start;
    gap: 7px;
    margin: 0 -4px;
    padding: 2px 4px 4px;
    overflow-x: auto;
    overscroll-behavior-inline: contain;
    scroll-snap-type: x proximity;
    scrollbar-width: none;
    -webkit-overflow-scrolling: touch;
  }
  nav::-webkit-scrollbar { display: none; }
  nav a {
    flex: 0 0 auto;
    min-height: 34px;
    scroll-snap-align: start;
  }
  .callout { align-items: flex-start; flex-direction: column; }
}

@media (max-width: 620px) {
  .container { width: min(100% - 28px, 1160px); }
  .feature-grid, .why-stack-grid { grid-template-columns: 1fr; }
  .section { padding: 68px 0; }
  .hero { padding: 62px 0; }
  .flow-card { padding: 18px; }
  .stack-concept-flow { padding: 16px; }
  .stack-node { grid-template-columns: 1fr; gap: 2px; }
  .layer-stack { padding: 14px; }
  .layer-row { grid-template-columns: 34px 1fr; }
  .layer-row small { grid-column: 2; }
  nav a {
    min-height: 32px;
    padding: 6px 9px;
    border-radius: 10px;
    font-size: .69rem;
  }
  .footer-inner { align-items: flex-start; flex-direction: column; }
  .footer-links { flex-wrap: wrap; }
}