/* ──────────────────────────────────────────────────────────────────────
   Helix — RWA protocol landing
   Palette: deep blue (#0a1d6b), white, red (#d72638). DNA-themed.
   Institutional feel, mobile-first responsive scaling.
   ────────────────────────────────────────────────────────────────────── */

:root {
  --blue:        #0a1d6b;
  --blue-deep:   #061256;
  --blue-soft:   #3a5cff;
  --blue-tint:   #eef1fa;
  --red:         #d72638;
  --red-deep:    #8a0f1f;
  --red-tint:    #fde8eb;
  --white:       #ffffff;
  --bg:          #fafbff;
  --surface:     #ffffff;
  --surface-alt: #eef1fa;
  --ink:         #0a1226;
  --ink-soft:    #4a5374;
  --ink-mute:    #6b7390;
  --line:        #dde2ef;
  --line-soft:   #e8ecf6;
  --shadow-1:    0 1px 2px rgba(10, 29, 107, .04), 0 4px 16px rgba(10, 29, 107, .06);
  --shadow-2:    0 10px 30px rgba(10, 29, 107, .14);
  --shadow-helix:0 30px 80px rgba(10, 29, 107, .22);
  --radius:      14px;
  --radius-lg:   20px;
  --max:         1120px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background:
    radial-gradient(1200px 600px at 80% -10%, rgba(58, 92, 255, .08), transparent 60%),
    radial-gradient(900px 500px at 0% 30%,   rgba(215, 38, 56, .05),  transparent 60%),
    var(--bg);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, 'Inter', 'Segoe UI', system-ui, sans-serif;
  font-size: 16px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  /* `clip` preserves position:sticky for child elements; `hidden` would break the whitepaper TOC stickiness. */
  overflow-x: clip;
}

a { color: inherit; text-decoration: none; }
img, svg { display: block; max-width: 100%; }

/* ── Header ──────────────────────────────────────────────────────── */
.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(250, 251, 255, .85);
  backdrop-filter: saturate(160%) blur(14px);
  -webkit-backdrop-filter: saturate(160%) blur(14px);
  border-bottom: 1px solid var(--line);
}
.header-inner {
  max-width: var(--max);
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: 18px;
  padding: 14px 24px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  letter-spacing: -0.01em;
}
.brand-mark {
  width: 30px;
  height: 30px;
  flex-shrink: 0;
}
.brand-name {
  font-size: 18px;
  color: var(--blue);
}
.brand-ticker {
  font-size: 10.5px;
  font-weight: 700;
  letter-spacing: 0.14em;
  color: var(--red);
  background: var(--red-tint);
  padding: 3px 7px;
  border-radius: 5px;
  margin-left: 2px;
}

.nav {
  display: flex;
  gap: 22px;
  margin-left: 12px;
  font-size: 14.5px;
  color: var(--ink-soft);
}
.nav a:hover { color: var(--blue); }
.header-inner .cta { margin-left: auto; }

/* ── CTA buttons ─────────────────────────────────────────────────── */
.cta {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 11px 22px;
  border-radius: 10px;
  font-weight: 600;
  font-size: 14.5px;
  letter-spacing: -0.005em;
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform .12s ease, background .12s ease, border-color .12s ease, box-shadow .12s ease;
  white-space: nowrap;
}
.cta-primary {
  background: var(--blue);
  color: var(--white);
  box-shadow: 0 1px 2px rgba(0, 0, 0, .05), 0 8px 22px rgba(10, 29, 107, .25);
}
.cta-primary:hover {
  background: var(--blue-deep);
  transform: translateY(-1px);
  box-shadow: 0 1px 2px rgba(0, 0, 0, .05), 0 12px 28px rgba(10, 29, 107, .32);
}
.cta-ghost {
  background: transparent;
  color: var(--blue);
  border: 1px solid var(--line);
}
.cta-ghost:hover {
  border-color: var(--blue);
}

/* ── Hero ────────────────────────────────────────────────────────── */
.hero {
  padding: 80px 24px 64px;
  max-width: var(--max);
  margin: 0 auto;
}
.hero-grid {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  align-items: center;
  gap: 48px;
}
.hero-copy { text-align: left; }

.badge {
  display: inline-flex;
  padding: 6px 14px;
  border-radius: 999px;
  background: var(--surface);
  border: 1px solid var(--line);
  font-size: 12.5px;
  color: var(--blue);
  letter-spacing: 0.02em;
  margin-bottom: 22px;
  box-shadow: var(--shadow-1);
  font-weight: 600;
}

.hero h1 {
  font-size: clamp(36px, 5.4vw, 64px);
  font-weight: 800;
  letter-spacing: -0.025em;
  line-height: 1.04;
  margin: 0 0 22px;
  color: var(--blue);
}
.hero h1 em {
  font-style: italic;
  color: var(--red);
  font-weight: 800;
}

.lede {
  max-width: 540px;
  margin: 0 0 30px;
  font-size: 17px;
  color: var(--ink-soft);
}

.hero-ctas {
  display: flex;
  gap: 12px;
  margin-bottom: 40px;
  flex-wrap: wrap;
}

.hero-stats {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
  max-width: 520px;
}
.hero-stats li {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px 14px;
  display: flex;
  flex-direction: column;
  gap: 4px;
  box-shadow: var(--shadow-1);
}
.stat-num {
  font-size: 20px;
  font-weight: 700;
  color: var(--blue);
  letter-spacing: -0.01em;
}
.stat-label {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-mute);
  font-weight: 600;
}

/* ── Hero art / helix ────────────────────────────────────────────── */
.hero-art {
  position: relative;
  display: grid;
  place-items: center;
  filter: drop-shadow(var(--shadow-helix));
}
.hero-art::before {
  content: '';
  position: absolute;
  inset: -10% -5% -10% -5%;
  background:
    radial-gradient(closest-side, rgba(58, 92, 255, .18), transparent 70%);
  z-index: -1;
  pointer-events: none;
}
.hero-art svg {
  width: 100%;
  max-width: 340px;
  height: auto;
  animation: helixFloat 8s ease-in-out infinite;
}
@keyframes helixFloat {
  0%, 100% { transform: translateY(0); }
  50%      { transform: translateY(-8px); }
}
@media (prefers-reduced-motion: reduce) {
  .hero-art svg { animation: none; }
}

/* ── Generic section ─────────────────────────────────────────────── */
.section {
  padding: 80px 24px;
  max-width: var(--max);
  margin: 0 auto;
}
.section-alt {
  background: var(--surface-alt);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  max-width: none;
  margin: 0;
  padding: 0;
}
.section-alt-inner {
  max-width: var(--max);
  margin: 0 auto;
  padding: 80px 24px;
}

.section-head { margin-bottom: 40px; }
.section-head h2 {
  font-size: clamp(26px, 4vw, 40px);
  font-weight: 800;
  letter-spacing: -0.02em;
  margin: 0 0 10px;
  color: var(--blue);
}
.section-head p {
  margin: 0;
  font-size: 16.5px;
  color: var(--ink-soft);
}

/* ── Asset classes grid ──────────────────────────────────────────── */
.asset-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 18px;
}
.asset-card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 28px 28px 22px;
  box-shadow: var(--shadow-1);
  transition: transform .15s ease, box-shadow .15s ease;
}
.asset-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-2);
}
.asset-tag {
  display: inline-block;
  font-size: 11.5px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 4px 10px;
  border-radius: 6px;
  margin-bottom: 14px;
}
.tag-blue {
  background: var(--blue-tint);
  color: var(--blue);
}
.tag-red {
  background: var(--red-tint);
  color: var(--red);
}
.asset-card h3 {
  font-size: 22px;
  font-weight: 700;
  margin: 0 0 10px;
  color: var(--ink);
  letter-spacing: -0.01em;
}
.asset-card p {
  margin: 0 0 18px;
  color: var(--ink-soft);
}
.asset-meta {
  margin: 0;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
  padding-top: 14px;
  border-top: 1px solid var(--line-soft);
}
.asset-meta dt {
  font-size: 11.5px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-mute);
  font-weight: 600;
}
.asset-meta dd {
  margin: 4px 0 0;
  font-weight: 700;
  font-size: 15px;
  color: var(--blue);
  letter-spacing: -0.005em;
}

/* ── How it works ────────────────────────────────────────────────── */
.how-strand {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
  position: relative;
}
.how-strand li {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 30px 28px;
  position: relative;
  box-shadow: var(--shadow-1);
}
.how-strand li:nth-child(1) { border-top: 3px solid var(--blue); }
.how-strand li:nth-child(2) { border-top: 3px solid var(--red); }
.how-strand li:nth-child(3) { border-top: 3px solid var(--blue); }

.rung {
  display: inline-block;
  font-size: 12.5px;
  font-weight: 800;
  letter-spacing: 0.14em;
  color: var(--blue);
  margin-bottom: 14px;
}
.how-strand li:nth-child(2) .rung { color: var(--red); }

.how-strand h3 {
  font-size: 22px;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin: 0 0 10px;
  color: var(--ink);
}
.how-strand p {
  margin: 0;
  color: var(--ink-soft);
}

/* ── Metrics ─────────────────────────────────────────────────────── */
.metric-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
}
.metric {
  background: linear-gradient(180deg, var(--blue), var(--blue-deep));
  color: var(--white);
  border-radius: var(--radius-lg);
  padding: 28px 26px;
  display: flex;
  flex-direction: column;
  gap: 4px;
  position: relative;
  overflow: hidden;
}
.metric::after {
  content: '';
  position: absolute;
  right: -30px;
  top: -30px;
  width: 90px;
  height: 90px;
  border: 2px solid rgba(255, 255, 255, .08);
  border-radius: 50%;
}
.metric:nth-child(3) {
  background: linear-gradient(180deg, var(--red), var(--red-deep));
}
.metric-num {
  font-size: 36px;
  font-weight: 800;
  letter-spacing: -0.02em;
}
.metric-label {
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: rgba(255, 255, 255, .82);
  font-weight: 600;
}

/* ── Why grid ────────────────────────────────────────────────────── */
.why-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
}
.why-card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 24px 22px;
  box-shadow: var(--shadow-1);
}
.why-card h3 {
  font-size: 16.5px;
  font-weight: 700;
  margin: 0 0 8px;
  color: var(--blue);
}
.why-card p {
  margin: 0;
  font-size: 14.5px;
  color: var(--ink-soft);
}

/* ── FAQ ─────────────────────────────────────────────────────────── */
.faq {
  display: flex;
  flex-direction: column;
  gap: 8px;
  max-width: 820px;
}
.faq details {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px 22px;
  transition: box-shadow .15s ease, border-color .15s ease;
}
.faq details[open] {
  box-shadow: var(--shadow-1);
  border-color: var(--blue-soft);
}
.faq summary {
  cursor: pointer;
  font-weight: 600;
  font-size: 15.5px;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
  color: var(--ink);
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after {
  content: '+';
  font-size: 22px;
  color: var(--ink-mute);
  font-weight: 400;
  margin-left: 12px;
  transition: transform .15s ease, color .15s ease;
}
.faq details[open] summary::after {
  transform: rotate(45deg);
  color: var(--red);
}
.faq p {
  margin: 12px 0 0;
  color: var(--ink-soft);
}

/* ── Footer ──────────────────────────────────────────────────────── */
.site-footer {
  background: var(--surface);
  border-top: 1px solid var(--line);
  padding: 36px 24px;
  font-size: 14px;
  color: var(--ink-soft);
}
.foot-row {
  max-width: var(--max);
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: 24px;
  flex-wrap: wrap;
  margin-bottom: 18px;
}
.foot-links {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  gap: 18px;
  margin-left: auto;
  flex-wrap: wrap;
}
.foot-links a:hover { color: var(--blue); }
.disclaimer {
  max-width: var(--max);
  margin: 0 auto;
  font-size: 12.5px;
  color: var(--ink-mute);
  line-height: 1.55;
}

/* ── Responsive ─────────────────────────────────────────────────── */

/* Tablet */
@media (max-width: 960px) {
  .header-inner { padding: 12px 20px; gap: 14px; }
  .nav { gap: 18px; margin-left: 6px; }
  .hero-grid { grid-template-columns: 1fr; gap: 32px; }
  .hero-art  { order: -1; }
  .hero-art svg { max-width: 260px; }
  .asset-grid { grid-template-columns: 1fr; }
  .how-strand { grid-template-columns: 1fr; }
  .metric-grid { grid-template-columns: repeat(2, 1fr); }
  .why-grid { grid-template-columns: repeat(2, 1fr); }
  .section, .section-alt-inner { padding: 64px 20px; }
  .hero { padding: 56px 20px 40px; }
}

/* Mobile */
@media (max-width: 640px) {
  .nav { display: none; }
  .header-inner { padding: 12px 16px; gap: 10px; }
  .brand-ticker { display: none; }
  .site-header .cta { padding: 9px 16px; font-size: 14px; }

  .hero { padding: 48px 16px 36px; text-align: center; }
  .hero-copy { text-align: center; }
  .hero-art { display: none; }  /* helix hidden on mobile per spec */
  .hero h1 { font-size: 34px; line-height: 1.08; }
  .lede { font-size: 16px; margin-left: auto; margin-right: auto; }
  .hero-ctas { justify-content: center; }
  .hero-stats {
    grid-template-columns: repeat(3, 1fr);
    margin: 0 auto;
  }
  .hero-stats li { padding: 12px 8px; }
  .stat-num { font-size: 17px; }
  .stat-label { font-size: 9.5px; letter-spacing: 0.06em; }

  .section, .section-alt-inner { padding: 56px 16px; }
  .section-head { margin-bottom: 28px; }
  .section-head h2 { font-size: 24px; }
  .section-head p { font-size: 15.5px; }

  .asset-card { padding: 22px 22px 18px; }
  .asset-card h3 { font-size: 19px; }
  .asset-meta dd { font-size: 14px; }

  .how-strand li { padding: 24px 22px; }
  .how-strand h3 { font-size: 19px; }

  .metric-grid { grid-template-columns: 1fr 1fr; gap: 12px; }
  .metric { padding: 22px 20px; }
  .metric-num { font-size: 28px; }
  .metric-label { font-size: 11px; }

  .why-grid { grid-template-columns: 1fr; }
  .why-card { padding: 20px 20px; }

  .faq details { padding: 14px 18px; }
  .faq summary { font-size: 15px; }

  .foot-row { flex-direction: column; align-items: flex-start; gap: 14px; }
  .foot-links { margin-left: 0; gap: 14px; font-size: 13.5px; }
}

/* Very narrow */
@media (max-width: 380px) {
  .hero h1 { font-size: 30px; }
  .hero-stats { grid-template-columns: 1fr 1fr; }
  .hero-stats li:nth-child(3) { grid-column: span 2; }
}