:root {
    --bg: #EDF1F5;
    --panel: #FFFFFF;
    --ink: #101826;
    --ink-soft: #57667A;
    --line: #C9D3DD;
    --line-soft: #DCE3EA;
    --accent: #E4572E;
    --accent-soft: #FBD9CB;
  }

  * { box-sizing: border-box; }

  html { scroll-behavior: smooth; }

  body {
    margin: 0;
    background: var(--bg);
    color: var(--ink);
    font-family: 'Space Grotesk', sans-serif;
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
  }

  /* faint blueprint grid */
  .grid-bg {
    background-image:
      linear-gradient(var(--line-soft) 1px, transparent 1px),
      linear-gradient(90deg, var(--line-soft) 1px, transparent 1px);
    background-size: 40px 40px;
  }

  a { color: inherit; }

  .wrap {
    max-width: 1080px;
    margin: 0 auto;
    padding: 0 28px;
  }

  .col {
    max-width: 680px;
  }

  code, .mono {
    font-family: 'IBM Plex Mono', monospace;
  }

  /* ---------- header ---------- */

  header {
    border-bottom: 1px solid var(--line);
  }

  .header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 22px 0;
  }

  .brand {
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 600;
    font-size: 18px;
    letter-spacing: -0.01em;
  }

  .brand .dot {
    width: 9px;
    height: 9px;
    border-radius: 50%;
    background: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-soft);
  }

  .header-links {
    display: flex;
    gap: 28px;
    font-family: 'IBM Plex Mono', monospace;
    font-size: 13px;
    color: var(--ink-soft);
  }

  .header-links a:hover { color: var(--ink); }

  /* ---------- hero ---------- */

  .hero {
    padding: 72px 0 56px;
    display: grid;
    grid-template-columns: 1.1fr 0.9fr;
    gap: 40px;
    align-items: center;
  }

  .kicker {
    font-family: 'IBM Plex Mono', monospace;
    font-size: 13px;
    color: var(--ink-soft);
    margin: 0 0 18px;
  }

  .kicker span { color: var(--accent); }

  h1 {
    font-size: 52px;
    line-height: 1.04;
    letter-spacing: -0.02em;
    margin: 0 0 20px;
    font-weight: 700;
  }

  .hero p.lede {
    font-size: 18px;
    color: var(--ink-soft);
    max-width: 480px;
    margin: 0 0 32px;
  }

  .cta-row {
    display: flex;
    gap: 14px;
    flex-wrap: wrap;
  }

  .btn {
    font-family: 'IBM Plex Mono', monospace;
    font-size: 13.5px;
    text-decoration: none;
    padding: 13px 20px;
    border-radius: 3px;
    display: inline-block;
    border: 1px solid transparent;
  }

  .btn-primary {
    background: var(--ink);
    color: #fff;
  }
  .btn-primary:hover { background: #26344A; }

  .btn-secondary {
    border-color: var(--line);
    color: var(--ink);
    background: transparent;
  }
  .btn-secondary:hover { border-color: var(--ink); }

  /* ---------- signal diagram ---------- */

  .scope {
    position: relative;
    aspect-ratio: 1 / 1;
    max-width: 340px;
    margin: 0 auto;
    border: 1px solid var(--line);
    border-radius: 50%;
    background: var(--panel);
  }

  .scope svg { width: 100%; height: 100%; display: block; }

  .sweep {
    transform-origin: 170px 170px;
    animation: sweep 4.5s linear infinite;
  }

  @keyframes sweep {
    from { transform: rotate(0deg); }
    to { transform: rotate(360deg); }
  }

  .ping {
    animation: ping 4.5s ease-out infinite;
  }
  .ping.p2 { animation-delay: 1.1s; }
  .ping.p3 { animation-delay: 2.4s; }

  @keyframes ping {
    0%   { opacity: 0; }
    4%   { opacity: 1; }
    30%  { opacity: 0.75; }
    100% { opacity: 0; }
  }

  @media (prefers-reduced-motion: reduce) {
    .sweep, .ping { animation: none; }
  }

  /* ---------- section shell ---------- */

  section {
    border-top: 1px solid var(--line);
    padding: 56px 0;
  }

  .section-head {
    display: grid;
    grid-template-columns: 200px 1fr;
    gap: 40px;
  }

  .section-num {
    font-family: 'IBM Plex Mono', monospace;
    font-size: 13px;
    color: var(--ink-soft);
    padding-top: 4px;
  }

  h2 {
    font-size: 26px;
    letter-spacing: -0.01em;
    margin: 0 0 18px;
    font-weight: 600;
  }

  section p {
    color: var(--ink-soft);
    font-size: 16px;
    margin: 0 0 16px;
  }

  /* ---------- code panel ---------- */

  .panel {
    background: var(--ink);
    color: #E8EAED;
    border-radius: 6px;
    padding: 22px 24px;
    font-family: 'IBM Plex Mono', monospace;
    font-size: 13.5px;
    line-height: 1.7;
    overflow-x: auto;
    white-space: pre;
  }

  .panel .c1 { color: #6B93B5; }
  .panel .c2 { color: #F0A868; }
  .panel .c3 { color: #9AE6C0; }

  .panel-label {
    font-family: 'IBM Plex Mono', monospace;
    font-size: 12px;
    color: var(--ink-soft);
    margin-bottom: 10px;
    display: flex;
    justify-content: space-between;
  }

  /* ---------- requirements / install two-up ---------- */

  .two-up {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 32px;
  }

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

  ul.req li {
    display: flex;
    gap: 12px;
    padding: 12px 0;
    border-top: 1px solid var(--line-soft);
    color: var(--ink-soft);
    font-size: 15px;
  }
  ul.req li:first-child { border-top: none; }

  ul.req li::before {
    content: "";
    width: 6px;
    height: 6px;
    margin-top: 8px;
    border-radius: 50%;
    background: var(--accent);
    flex-shrink: 0;
  }

  /* ---------- steps ---------- */

  .steps {
    counter-reset: step;
    display: flex;
    flex-direction: column;
  }

  .step {
    display: grid;
    grid-template-columns: 44px 1fr;
    gap: 18px;
    padding: 20px 0;
    border-top: 1px solid var(--line-soft);
  }
  .step:first-child { border-top: none; padding-top: 0; }

  .step-num {
    counter-increment: step;
    font-family: 'IBM Plex Mono', monospace;
    font-size: 14px;
    color: var(--accent);
    padding-top: 2px;
  }
  .step-num::before {
    content: counter(step, decimal-leading-zero);
  }

  .step h3 {
    font-size: 16px;
    margin: 0 0 6px;
    font-weight: 600;
  }
  .step p {
    margin: 0;
    font-size: 15px;
  }

  /* ---------- notes ---------- */

  .notes-box {
    border: 1px dashed var(--line);
    border-radius: 6px;
    padding: 20px 22px;
    background: var(--panel);
  }
  .notes-box p { margin: 0; color: var(--ink-soft); }
  .notes-box .tag {
    font-family: 'IBM Plex Mono', monospace;
    font-size: 12px;
    color: var(--accent);
    display: block;
    margin-bottom: 10px;
  }

  /* ---------- footer ---------- */

  footer {
    border-top: 1px solid var(--line);
    padding: 40px 0 56px;
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
    flex-wrap: wrap;
    gap: 20px;
  }

  footer .foot-left p {
    margin: 0;
    font-family: 'IBM Plex Mono', monospace;
    font-size: 13px;
    color: var(--ink-soft);
  }

  footer .foot-links {
    display: flex;
    gap: 22px;
    font-family: 'IBM Plex Mono', monospace;
    font-size: 13px;
  }
  footer .foot-links a { color: var(--ink-soft); text-decoration: none; }
  footer .foot-links a:hover { color: var(--ink); }

  /* ---------- responsive ---------- */

  @media (max-width: 820px) {
    .hero { grid-template-columns: 1fr; }
    .scope { order: -1; max-width: 240px; }
    h1 { font-size: 38px; }
    .section-head { grid-template-columns: 1fr; gap: 12px; }
    .two-up { grid-template-columns: 1fr; }
  }