:root {
  --night: #05080c;
  --night-2: #0a1218;
  --ink: #d7eef2;
  --mute: #7a99a3;
  --cyan: #3ec8d8;
  --cyan-2: #7ee7f0;
  --hold: #e23b3b;
  --pass: #1f8a6e;
  --line: rgba(62, 200, 216, 0.18);
  --glass: rgba(10, 18, 24, 0.62);
  --serif: "Noto Serif SC", "Songti SC", serif;
  --sans: "Noto Sans SC", "PingFang SC", sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, Menlo, monospace;
  --shadow: 0 28px 64px rgba(0, 0, 0, 0.45);
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

section[id] {
  scroll-margin-top: 84px;
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--night);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.75;
}

img {
  max-width: 100%;
  display: block;
}

a {
  color: inherit;
  text-decoration: none;
}

.app-link {
  color: var(--cyan-2);
  text-decoration: underline;
  text-underline-offset: 3px;
}

button {
  font-family: inherit;
  cursor: pointer;
}

code {
  font-family: var(--mono);
  font-size: 0.9em;
  background: rgba(62, 200, 216, 0.12);
  padding: 0.05em 0.4em;
}

.grain {
  pointer-events: none;
  position: fixed;
  inset: 0;
  z-index: 40;
  opacity: 0.1;
  background-image: url("images/texture.webp");
  background-size: 480px auto;
  mix-blend-mode: overlay;
}

.skip {
  position: absolute;
  left: -999px;
}

.skip:focus {
  left: 12px;
  top: 12px;
  z-index: 60;
  background: var(--night-2);
  padding: 8px 12px;
}

.nav {
  position: sticky;
  top: 0;
  z-index: 30;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 12px 28px;
  background: var(--glass);
  backdrop-filter: blur(18px) saturate(1.4);
  border-bottom: 1px solid var(--line);
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--serif);
  font-weight: 700;
  letter-spacing: 0.06em;
}

.brand small {
  display: block;
  font-family: var(--mono);
  font-weight: 400;
  font-size: 10px;
  letter-spacing: 0.16em;
  color: var(--mute);
}

.seal {
  width: 40px;
  height: 40px;
  display: grid;
  place-items: center;
  border: 1px solid var(--cyan);
  color: var(--cyan);
  border-radius: 10px;
  font-family: var(--mono);
  font-size: 13px;
}

.nav-toggle {
  display: none;
  background: transparent;
  border: 1px solid var(--cyan);
  color: var(--cyan);
  padding: 6px 12px;
}

.nav-links {
  display: flex;
  gap: 16px;
  font-size: 13px;
}

.nav-links a {
  color: var(--mute);
  border-bottom: 1px solid transparent;
  padding-bottom: 2px;
}

.nav-links a.is-active,
.nav-links a:hover {
  color: var(--cyan-2);
  border-bottom-color: var(--cyan);
}

.nav-links a.live {
  color: var(--night);
  background: var(--cyan);
  border: 0;
  padding: 6px 12px;
  border-radius: 4px;
}

.hero {
  position: relative;
  min-height: 94vh;
  display: grid;
  align-items: end;
  overflow: hidden;
}

.hero img {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.hero::after {
  content: "";
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse at 20% 30%, rgba(62, 200, 216, 0.18), transparent 46%),
    linear-gradient(180deg, rgba(5, 8, 12, 0.2) 0%, rgba(5, 8, 12, 0.55) 48%, rgba(5, 8, 12, 0.96) 100%);
}

.hero-inner {
  position: relative;
  z-index: 1;
  padding: 8vh 8vw 10vh;
  max-width: 920px;
}

.kicker,
.vlabel {
  font-family: var(--mono);
  letter-spacing: 0.22em;
  font-size: 11px;
  color: var(--cyan);
  margin: 0 0 12px;
}

.vlabel {
  color: var(--cyan-2);
}

h1,
h2,
h3 {
  font-family: var(--serif);
  font-weight: 700;
  line-height: 1.08;
  margin: 0 0 16px;
}

h1 {
  font-size: clamp(44px, 8vw, 96px);
  letter-spacing: -0.03em;
}

h2 {
  font-size: clamp(28px, 4vw, 44px);
}

h3 {
  font-size: 22px;
}

.lead {
  font-size: 18px;
  max-width: 46em;
  color: rgba(215, 238, 242, 0.86);
}

.meta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 22px 0;
}

.chip {
  border: 1px solid rgba(62, 200, 216, 0.35);
  padding: 4px 10px;
  font-size: 12px;
  letter-spacing: 0.08em;
  font-family: var(--mono);
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 10px 18px;
  border: 1px solid currentColor;
  font-size: 14px;
}

.btn-fill {
  background: var(--cyan);
  color: var(--night);
  border-color: var(--cyan);
}

.btn-ghost {
  background: transparent;
  color: inherit;
}

.wrap {
  width: min(1120px, calc(100% - 48px));
  margin: 0 auto;
  padding: 88px 0;
}

.section-head {
  display: grid;
  grid-template-columns: 160px 1fr;
  gap: 24px;
  margin-bottom: 40px;
}

.section-head p:last-child {
  color: var(--mute);
  margin: 0;
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
}

.card,
.bench,
.io-grid > div {
  background: rgba(10, 18, 24, 0.72);
  border: 1px solid var(--line);
  padding: 22px 22px 18px;
  backdrop-filter: blur(12px);
}

.card {
  min-height: 220px;
}

.stamp {
  display: inline-block;
  font-size: 11px;
  letter-spacing: 0.16em;
  color: var(--cyan);
  border: 1px solid var(--cyan);
  padding: 2px 8px;
  margin-bottom: 10px;
  font-family: var(--mono);
}

.card ul,
.io-grid ul,
.rule-list {
  margin: 0;
  padding-left: 1.1em;
}

.card li,
.io-grid li,
.rule-list li {
  margin: 0.35em 0;
}

.alt {
  background: linear-gradient(180deg, #071016 0%, var(--night) 100%);
}

.step {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 36px;
  align-items: center;
  margin-bottom: 72px;
}

.step.reverse {
  direction: rtl;
}

.step.reverse > * {
  direction: ltr;
}

.num {
  font-family: var(--mono);
  font-size: 13px;
  letter-spacing: 0.2em;
  color: var(--cyan);
  display: block;
  margin-bottom: 8px;
}

figure {
  margin: 0;
}

figure img {
  width: 100%;
  height: 340px;
  object-fit: cover;
  box-shadow: var(--shadow);
}

figcaption {
  margin-top: 10px;
  font-size: 13px;
  color: var(--mute);
}

.o2-demo {
  margin-top: 22px;
  padding: 16px;
  border: 1px solid var(--line);
  background: rgba(226, 59, 59, 0.06);
}

.clock-label {
  margin: 0 0 8px;
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--mute);
  font-family: var(--mono);
}

.o2-read {
  display: flex;
  align-items: baseline;
  gap: 10px;
  margin-bottom: 10px;
}

.o2-read strong {
  font-family: var(--mono);
  font-size: 48px;
  font-weight: 500;
  line-height: 1;
}

.clock-track {
  height: 8px;
  background: rgba(215, 238, 242, 0.08);
  overflow: hidden;
}

.clock-track i {
  display: block;
  height: 100%;
  width: 70%;
  background: var(--hold);
}

.clock-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 12px;
  gap: 12px;
  font-size: 13px;
}

.lock-bad {
  color: var(--hold);
  font-family: var(--mono);
}

.lock-ok {
  color: var(--pass);
  font-family: var(--mono);
}

.clock-meta .btn {
  color: var(--cyan);
  border-color: var(--cyan);
  padding: 6px 12px;
}

.bench-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
}

.bench h3 {
  font-size: 18px;
  margin-bottom: 8px;
}

.bench p {
  margin: 0;
  color: var(--mute);
  font-size: 14px;
}

.rule-list {
  font-size: 17px;
  max-width: 46em;
}

.io-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 28px;
}

footer {
  border-top: 1px solid var(--line);
  background: #020406;
  color: var(--mute);
}

.footer-inner {
  padding: 32px 0;
  display: flex;
  justify-content: space-between;
  gap: 16px;
  font-size: 13px;
}

@media (max-width: 1024px) {
  .nav-toggle {
    display: inline-flex !important;
    color: var(--cyan-2);
    border-color: var(--cyan-2);
  }

  .nav-links {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex-direction: column;
    padding: 12px 20px 18px;
    background: var(--night);
    border-bottom: 1px solid var(--line);
  }

  .nav-links.open {
    display: flex;
  }

  .section-head,
  .grid-3,
  .step,
  .step.reverse,
  .io-grid,
  .bench-grid {
    grid-template-columns: 1fr;
    direction: ltr;
  }

  .footer-inner {
    flex-direction: column;
  }

  h1 {
    font-size: 42px;
  }

  .o2-read strong {
    font-size: 36px;
  }

  figure img {
    height: 220px;
  }

  .wrap {
    width: min(1120px, calc(100% - 32px));
    padding: 56px 0;
  }
}