:root {
  --ice: #071820;
  --ice-2: #0e2a36;
  --cyan: #7ec8d6;
  --cyan-2: #b7e6ee;
  --straw: #d6b15a;
  --fail: #d9784a;
  --ok: #5aa882;
  --paper: #e8f2f4;
  --ink: #0e2a36;
  --mute: #5b7380;
  --display: "Space Grotesk", "Noto Sans SC", sans-serif;
  --sans: "Noto Sans SC", "PingFang SC", sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, Menlo, monospace;
}

*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
section[id] { scroll-margin-top: 88px; }

body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.65;
}

img { max-width: 100%; display: block; }
a { color: inherit; text-decoration: none; }
.app-link { color: #1a6b7a; text-decoration: underline; text-underline-offset: 3px; }
button { font-family: inherit; cursor: pointer; }
code { font-family: var(--mono); background: rgba(126, 200, 214, 0.25); padding: 0.05em 0.35em; }

.frost {
  pointer-events: none;
  position: fixed;
  inset: 0;
  z-index: 8;
  opacity: 0.14;
  background-image: url("images/texture.webp");
  background-size: 280px auto;
  mix-blend-mode: soft-light;
}

.skip { position: absolute; left: -999px; }
.skip:focus { left: 10px; top: 10px; z-index: 80; background: var(--cyan); padding: 8px; }

.frost-bar {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 10px 20px;
  background: rgba(7, 24, 32, 0.92);
  color: var(--cyan-2);
  border-bottom: 1px solid rgba(126, 200, 214, 0.3);
}
.brand { font-family: var(--display); letter-spacing: 0.04em; }
.brand small { display: block; font-family: var(--mono); font-size: 10px; letter-spacing: 0.14em; color: var(--cyan); font-weight: 400; }
.nav-toggle { display: none; background: var(--cyan); color: var(--ice); border: 0; padding: 8px 12px; font-weight: 700; }
.belt-nav { display: flex; gap: 14px; align-items: center; font-size: 13px; }
.belt-nav a { color: #8fb8c2; }
.belt-nav a.is-active, .belt-nav a:hover { color: var(--cyan-2); }
.belt-nav a.live { background: var(--cyan); color: var(--ice); padding: 7px 12px; font-weight: 700; }

.zones {
  list-style: none;
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  margin: 0;
  padding: 0;
  background: var(--ice);
  color: var(--cyan-2);
  font-family: var(--mono);
  font-size: 12px;
}
.zones .z {
  padding: 10px 8px;
  border-right: 1px solid rgba(126, 200, 214, 0.25);
  text-align: center;
}
.zones .z small { display: block; color: var(--cyan); margin-top: 4px; }
.zones .z.on { background: #123844; }
.zones .z.warn { background: #3a2a12; color: var(--straw); }

.tunnel-hero {
  position: relative;
  min-height: 78vh;
  display: grid;
  align-items: end;
  color: var(--cyan-2);
}
.tunnel-hero > img { position: absolute; inset: 0; width: 100%; height: 100%; object-fit: cover; }
.tunnel-hero::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(90deg, rgba(7, 24, 32, 0.88) 0%, rgba(7, 24, 32, 0.35) 70%);
}
.tunnel-copy { position: relative; z-index: 1; padding: 8vh 6vw 8vh; max-width: 760px; }
.kicker { font-family: var(--mono); letter-spacing: 0.16em; font-size: 11px; color: var(--cyan); margin: 0 0 12px; }
h1, h2, h3 { font-family: var(--display); margin: 0 0 14px; line-height: 1.08; }
h1 { font-size: clamp(34px, 5.6vw, 68px); }
h2 { font-size: clamp(24px, 3vw, 38px); }
h3 { font-size: 20px; }
.lead { max-width: 44em; }
.quiet { color: var(--mute); max-width: 46em; }

.core-demo { margin: 18px 0; padding: 14px; background: rgba(7, 24, 32, 0.55); border: 1px solid rgba(126, 200, 214, 0.35); }
.lever { display: flex; align-items: center; gap: 10px; font-family: var(--mono); font-size: 12px; }
.lever input { flex: 1; accent-color: var(--cyan); }
#core-state { margin: 8px 0 0; }
.fail { color: var(--fail); }
.ok { color: var(--ok); }
.cta { display: flex; flex-wrap: wrap; gap: 10px; }
.btn { display: inline-flex; align-items: center; padding: 10px 14px; border: 1px solid currentColor; font-weight: 700; }
.btn.fill { background: var(--cyan); color: var(--ice); border-color: var(--cyan); }
.btn.ghost { color: #fff; }

.duct { width: min(1100px, calc(100% - 40px)); margin: 0 auto; padding: 72px 0; }
.ice { background: var(--ice); color: var(--cyan-2); }
.ice .quiet, .ice .kicker { color: var(--cyan); }
.ice .app-link { color: var(--cyan-2); }
.ice code { color: var(--paper); }

.tri { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; margin-top: 28px; }
.tri article, .grid6 article, .grid3 article, .io > div {
  background: #f3fbfc;
  border: 1px solid rgba(14, 42, 54, 0.12);
  padding: 16px;
}
.tri .dry { background: #f3e6c4; }
.tri ul, .io ul, .bound { margin: 0; padding-left: 1.1em; }
.tri li, .io li, .bound li { margin: 0 0 6px; }

.seg {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
  align-items: center;
  margin: 32px 0;
  padding-bottom: 12px;
  border-bottom: 1px dashed rgba(126, 200, 214, 0.3);
}
.seg.rev { direction: rtl; }
.seg.rev > * { direction: ltr; }
.num { font-family: var(--mono); color: var(--cyan); letter-spacing: 0.12em; font-size: 12px; }
.seg figure { margin: 0; }
.seg img { border: 1px solid rgba(126, 200, 214, 0.35); }
.seg figcaption { margin-top: 8px; font-size: 13px; color: var(--cyan); }

.dens-btns { display: flex; flex-wrap: wrap; gap: 8px; }
.dens-btns button {
  background: transparent;
  color: var(--cyan-2);
  border: 1px solid var(--cyan);
  padding: 8px 10px;
}
.dens-btns button.on { background: var(--cyan); color: var(--ice); }

.grid6, .grid3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; margin-top: 28px; }
.ice .grid3 article, .ice .io > div { background: var(--ice-2); color: var(--cyan-2); }
.io { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin-top: 24px; }
.bound { max-width: 46em; }

footer {
  padding: 18px 22px 36px;
  background: var(--ice);
  color: var(--cyan);
  font-family: var(--mono);
  font-size: 12px;
}

@media (max-width: 900px) {
  .zones { grid-template-columns: repeat(3, 1fr); }
  .tri, .seg, .seg.rev, .grid6, .grid3, .io { grid-template-columns: 1fr; }
  .seg.rev { direction: ltr; }
  .nav-toggle { display: inline-block; }
  .belt-nav {
    display: none;
    position: absolute;
    right: 10px;
    top: 52px;
    flex-direction: column;
    background: var(--ice);
    border: 1px solid var(--cyan);
    padding: 10px;
    min-width: 180px;
  }
  .belt-nav.open { display: flex; }
}