:root {
  --paper: #efece3;
  --ink: #161814;
  --mute: #5c6156;
  --line: #cfc9b8;
  --lime: #b7f34a;
  --night: #121513;
  --serif: "Songti SC", "STSong", "Noto Serif SC", "Georgia", "Times New Roman", serif;
  --sans: "PingFang SC", "Hiragino Sans GB", "Noto Sans SC", "Microsoft YaHei", sans-serif;
  --mono: "SF Mono", "Menlo", "IBM Plex Mono", ui-monospace, monospace;
  --pad: clamp(20px, 4vw, 56px);
  --max: 1120px;
}

* { box-sizing: border-box; }

html {
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

body {
  margin: 0;
  min-height: 100vh;
  background-image:
    linear-gradient(90deg, rgba(22, 24, 20, 0.035) 1px, transparent 1px),
    linear-gradient(rgba(22, 24, 20, 0.03) 1px, transparent 1px);
  background-size: 48px 48px;
}

.spine {
  position: fixed;
  inset: 0 auto 0 0;
  width: 12px;
  background: var(--lime);
  z-index: 8;
}

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

.skip:focus {
  left: 28px;
  top: 12px;
  z-index: 20;
  background: var(--night);
  color: var(--lime);
  padding: 8px 12px;
}

a {
  color: inherit;
}

.nav,
footer,
.hero,
.pair,
.spec,
.steps,
.band-inner {
  width: min(var(--max), calc(100% - var(--pad) * 2));
  margin-inline: auto;
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 28px 0;
  border-bottom: 1px solid var(--ink);
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  font-family: var(--mono);
  font-size: 0.78rem;
  letter-spacing: 0.22em;
  text-transform: uppercase;
}

.nav nav {
  display: flex;
  align-items: center;
  gap: 28px;
  font-family: var(--mono);
  font-size: 0.75rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.nav nav a {
  text-decoration: none;
}

.nav nav a:hover {
  color: #3d4a12;
}

.nav nav a:focus-visible,
.lang:focus-visible,
.btn:focus-visible,
.copy:focus-visible {
  outline: 2px solid var(--ink);
  outline-offset: 3px;
}

.copy:focus-visible {
  outline-color: var(--lime);
}

.lang {
  margin: 0;
  border: 1px solid var(--ink);
  background: transparent;
  font: inherit;
  letter-spacing: 0.14em;
  padding: 6px 10px;
  cursor: pointer;
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1.35fr) minmax(220px, 0.75fr);
  gap: 48px 56px;
  align-items: end;
  padding: 64px 0 72px;
  position: relative;
}

.hero::before {
  content: "K";
  position: absolute;
  right: -4%;
  top: -8%;
  font-family: var(--serif);
  font-size: clamp(12rem, 28vw, 22rem);
  line-height: 0.8;
  color: rgba(22, 24, 20, 0.06);
  pointer-events: none;
  font-weight: 700;
}

.kicker {
  margin: 0 0 16px;
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--mute);
}

.kicker.light {
  color: #9aa392;
}

h1,
h2 {
  font-family: var(--serif);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 0.98;
}

h1 {
  margin: 0 0 28px;
  font-size: clamp(3.4rem, 9vw, 6.4rem);
}

h1 em {
  font-style: normal;
  font-weight: 700;
  background: linear-gradient(var(--lime), var(--lime)) 0 88% / 100% 0.28em no-repeat;
}

html[lang="en"] {
  --serif: Georgia, "Times New Roman", serif;
}

html[lang="en"] h1 em {
  font-style: italic;
  font-weight: 600;
}

h2 {
  margin: 0 0 18px;
  font-size: clamp(2rem, 4vw, 2.8rem);
}

.lede {
  margin: 0 0 32px;
  max-width: 36em;
  color: var(--mute);
  font-size: 1.02rem;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  padding: 0 22px;
  text-decoration: none;
  font-family: var(--mono);
  font-size: 0.75rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.btn-solid {
  background: var(--night);
  color: var(--lime);
}

.btn-solid:hover {
  background: #000;
}

.btn-line {
  border: 1px solid var(--ink);
}

.btn-line:hover {
  background: var(--lime);
  border-color: var(--lime);
}

.stamp {
  position: relative;
  z-index: 1;
  background: var(--lime);
  color: var(--night);
  min-height: 320px;
  padding: 28px 24px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  box-shadow: 18px 18px 0 var(--night);
}

.stamp img {
  border-radius: 20px;
}

.led {
  display: flex;
  align-items: center;
  gap: 8px;
  margin: 0;
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.led i {
  width: 8px;
  height: 8px;
  background: var(--night);
  border-radius: 50%;
  animation: pulse 1.8s ease-out infinite;
}

.stamp p:last-child {
  margin: 0;
  font-family: var(--serif);
  font-size: 1.55rem;
  line-height: 1.15;
  font-weight: 600;
}

.band {
  background: var(--night);
  color: var(--paper);
  width: 100%;
  padding: 56px 0 48px;
  scroll-margin-top: 12px;
}

.band-inner {
  margin-inline: auto;
}

.band h2 {
  color: var(--paper);
}

.band p {
  color: #b7bbae;
  max-width: 34em;
}

.cmd {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin: 28px 0 18px;
  padding: 22px 22px;
  border: 1px solid #3a4333;
  background: #0c0e0c;
}

.cmd pre {
  margin: 0;
  flex: 1;
  min-width: 0;
  overflow-x: auto;
}

.cmd code {
  display: block;
  font-family: var(--mono);
  font-size: clamp(0.88rem, 2vw, 1.15rem);
  line-height: 1.55;
  white-space: pre;
  color: var(--lime);
}

.copy {
  flex: none;
  border: 1px solid #5c664c;
  background: transparent;
  color: var(--lime);
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  padding: 10px 12px;
  cursor: pointer;
}

.copy:hover,
.copy.is-done {
  background: var(--lime);
  color: var(--night);
  border-color: var(--lime);
}

.copy.is-fail {
  border-color: #c45c4a;
  color: #f0c4bc;
}

.ports {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 28px;
  margin: 0;
  font-family: var(--mono);
  font-size: 0.75rem;
  letter-spacing: 0.04em;
  color: #9aa392;
}

.pair {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  border-bottom: 1px solid var(--ink);
}

.pair article {
  padding: 56px 48px 56px 0;
}

.pair article:first-child {
  border-right: 1px solid var(--ink);
  padding-right: 48px;
}

.pair article:last-child {
  padding-left: 48px;
}

.pair ul {
  margin: 0;
  padding: 0;
  list-style: none;
}

.pair li {
  padding: 16px 0;
  border-top: 1px solid var(--line);
  color: var(--mute);
}

.pair li:last-child {
  border-bottom: 1px solid var(--line);
}

.spec {
  padding: 56px 0 8px;
}

.spec dl {
  display: grid;
  grid-template-columns: 1fr 1fr;
  margin: 12px 0 0;
  border-top: 1px solid var(--ink);
}

.spec div {
  padding: 28px 32px 36px 0;
  border-bottom: 1px solid var(--line);
  counter-increment: spec;
}

.spec div:nth-child(odd) {
  padding-right: 36px;
  border-right: 1px solid var(--line);
}

.spec dt {
  font-family: var(--serif);
  font-size: 1.8rem;
  margin: 0 0 10px;
  display: flex;
  gap: 14px;
  align-items: baseline;
}

.spec dt::before {
  content: counter(spec, decimal-leading-zero);
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.12em;
  color: var(--mute);
}

.spec dd {
  margin: 0;
  color: var(--mute);
}

.spec dl {
  counter-reset: spec;
}

.steps {
  padding: 56px 0 80px;
}

.steps ol {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0;
  margin: 8px 0 0;
  padding: 0;
  list-style: none;
  counter-reset: step;
  border-top: 1px solid var(--ink);
}

.steps li {
  counter-increment: step;
  padding: 24px 24px 8px 0;
  color: var(--mute);
}

.steps li::before {
  content: counter(step, decimal-leading-zero);
  display: block;
  margin-bottom: 14px;
  color: var(--ink);
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.14em;
}

footer {
  padding: 0 0 48px;
  border-top: 1px solid var(--ink);
  padding-top: 28px;
  font-family: var(--mono);
  font-size: 0.75rem;
  letter-spacing: 0.04em;
  color: var(--mute);
}

footer a {
  text-decoration: none;
  color: var(--ink);
}

.fine {
  max-width: 40em;
}

@keyframes pulse {
  50% { opacity: 0.25; }
}

@media (max-width: 860px) {
  .hero,
  .pair,
  .spec dl,
  .steps ol {
    grid-template-columns: 1fr;
  }

  .hero {
    padding-top: 36px;
  }

  .stamp {
    min-height: 220px;
    box-shadow: 10px 10px 0 var(--night);
  }

  .pair article,
  .pair article:first-child,
  .pair article:last-child {
    padding: 36px 0;
    border-right: 0;
  }

  .pair article:first-child {
    border-bottom: 1px solid var(--ink);
  }

  .spec div:nth-child(odd) {
    padding-right: 0;
    border-right: 0;
  }

  .cmd {
    flex-direction: column;
    align-items: flex-start;
  }
}

@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; }
}