:root{
      /* Light-first "lab notebook" theme */
      --bg: #fbfbf8;
      --paper: #ffffff;
      --ink: #10131a;
      --muted: #4a5568;
      --faint: #6b7280;

      --line: rgba(16,19,26,.10);
      --line2: rgba(16,19,26,.14);

      --accent: #1f6feb;     /* atlas blue */
      --accent2: #0ea5a4;    /* teal */
      --accent3: #f97316;    /* orange */

      --shadow: 0 20px 50px rgba(15, 23, 42, .10);
      --shadow2: 0 10px 24px rgba(15, 23, 42, .08);

      --radius: 16px;
      --radius2: 22px;

      --mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
      --sans: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial;
    }

    [data-theme="dark"]{
      --bg: #0b1020;
      --paper: rgba(255,255,255,.06);
      --ink: rgba(255,255,255,.92);
      --muted: rgba(255,255,255,.70);
      --faint: rgba(255,255,255,.55);
      --line: rgba(255,255,255,.10);
      --line2: rgba(255,255,255,.14);
      --shadow: 0 24px 80px rgba(0,0,0,.45);
      --shadow2: 0 16px 45px rgba(0,0,0,.35);
    }

    *{ box-sizing:border-box; }
    html,body{ height:100%; }
    body{
      margin:0;
      font-family: var(--sans);
      color: var(--ink);
      background:
        linear-gradient(var(--line) 1px, transparent 1px),
        linear-gradient(90deg, var(--line) 1px, transparent 1px),
        radial-gradient(900px 600px at 20% 0%, color-mix(in srgb, var(--accent) 10%, transparent), transparent 60%),
        radial-gradient(900px 600px at 100% 20%, color-mix(in srgb, var(--accent2) 10%, transparent), transparent 60%),
        var(--bg);
      background-size: 36px 36px, 36px 36px, auto, auto, auto;
      line-height: 1.45;
      letter-spacing: .2px;
    }

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

    .wrap{
      width:min(1200px, calc(100% - 48px));
      margin-inline:auto;
    }

    /* Top bar (clean, minimal) */
    .topbar{
      position: sticky;
      top: 0;
      z-index: 50;
      background: color-mix(in srgb, var(--bg) 86%, transparent);
      -webkit-backdrop-filter: blur(10px);
              backdrop-filter: blur(10px);
      border-bottom: 1px solid var(--line);
    }
    .topbar-inner{
      display:flex;
      align-items:center;
      justify-content:space-between;
      gap: 14px;
      padding: 12px 0;
    }

    .brand{
      display:flex;
      align-items:center;
      gap: 12px;
      min-width: 220px;
    }
    .mark{
      width: 34px;
      height: 34px;
      border-radius: 10px;
      background: conic-gradient(from 220deg, var(--accent), var(--accent2), var(--accent3), var(--accent));
      border: 1px solid var(--line2);
      box-shadow: var(--shadow2);
      position: relative;
      overflow:hidden;
    }
    .mark:before{
      content:"";
      position:absolute;
      inset: 7px;
      border-radius: 8px;
      background: color-mix(in srgb, var(--bg) 70%, transparent);
      border: 1px solid var(--line);
    }

    .brand strong{
      font-weight: 850;
      letter-spacing: -0.2px;
    }
    .brand span{
      display:block;
      font-size: 12px;
      color: var(--muted);
      font-family: var(--mono);
      margin-top: 2px;
    }

    .top-actions{
      display:flex;
      align-items:center;
      gap: 10px;
    }

    .btn{
      display:inline-flex;
      align-items:center;
      justify-content:center;
      gap: 8px;
      padding: 9px 12px;
      border-radius: 999px;
      border: 1px solid var(--line2);
      background: color-mix(in srgb, var(--paper) 88%, transparent);
      box-shadow: none;
      color: var(--ink);
      font-weight: 650;
      font-size: 13px;
      cursor:pointer;
      transition: transform .12s ease, background .12s ease, border-color .12s ease;
      -webkit-user-select: none;
         -moz-user-select: none;
          -ms-user-select: none;
              user-select: none;
    }
    .btn:hover{
      transform: translateY(-1px);
      border-color: color-mix(in srgb, var(--accent) 35%, var(--line2));
      background: color-mix(in srgb, var(--paper) 100%, transparent);
    }
    .btn.primary{
      background: linear-gradient(90deg, color-mix(in srgb, var(--accent) 20%, var(--paper)), color-mix(in srgb, var(--accent2) 16%, var(--paper)));
      border-color: color-mix(in srgb, var(--accent) 30%, var(--line2));
    }

    /* Layout: left rail + content */
    .layout{
      display:grid;
      grid-template-columns: 260px 1fr;
      gap: 18px;
      padding: 22px 0 44px;
      align-items:start;
    }

    .rail{
      position: sticky;
      top: 66px;
      border: 1px solid var(--line);
      background: color-mix(in srgb, var(--paper) 92%, transparent);
      border-radius: var(--radius2);
      box-shadow: var(--shadow2);
      overflow:hidden;
    }

    .rail-head{
      padding: 14px 14px 12px;
      border-bottom: 1px solid var(--line);
      background: linear-gradient(180deg, color-mix(in srgb, var(--paper) 96%, transparent), transparent);
    }
    .rail-head .k{
      font-family: var(--mono);
      font-size: 11px;
      color: var(--muted);
      letter-spacing: .6px;
      text-transform: uppercase;
    }
    .rail-head .t{
      margin-top: 6px;
      font-size: 13px;
      color: var(--muted);
    }

    .rail-nav{
      padding: 10px;
      display:flex;
      flex-direction:column;
      gap: 6px;
    }
    .rail-nav a{
      display:flex;
      align-items:center;
      justify-content:space-between;
      gap: 10px;
      padding: 10px 10px;
      border-radius: 12px;
      color: var(--muted);
      border: 1px solid transparent;
      transition: background .12s ease, border-color .12s ease, color .12s ease;
      font-size: 13px;
    }
    .rail-nav a:hover{
      background: color-mix(in srgb, var(--accent) 8%, transparent);
      border-color: var(--line);
      color: var(--ink);
    }
    .rail-nav a.active{
      background: color-mix(in srgb, var(--accent) 12%, transparent);
      border-color: color-mix(in srgb, var(--accent) 25%, var(--line));
      color: var(--ink);
    }
    .rail-nav .tag{
      font-family: var(--mono);
      font-size: 11px;
      color: var(--faint);
      border: 1px solid var(--line);
      padding: 3px 8px;
      border-radius: 999px;
      background: color-mix(in srgb, var(--paper) 85%, transparent);
    }

    /* Main content */
    .content{
      display:flex;
      flex-direction:column;
      gap: 14px;
    }

    .panel{
      border: 1px solid var(--line);
      background: color-mix(in srgb, var(--paper) 92%, transparent);
      border-radius: var(--radius2);
      box-shadow: var(--shadow);
      overflow:hidden;
    }
    .panel-inner{ padding: 18px; }

    /* Hero: editorial + system map */
    .hero{
      position:relative;
    }

    .hero-top{
      display:grid;
      grid-template-columns: 1.1fr .9fr;
      gap: 14px;
      align-items:stretch;
    }

    .hero h1{
      margin: 0;
      font-size: clamp(30px, 3.6vw, 46px);
      line-height: 1.06;
      letter-spacing: -0.8px;
    }

    .lead{
      margin: 10px 0 0;
      color: var(--muted);
      font-size: 15px;
      max-width: 62ch;
    }

    .hero-meta{
      display:flex;
      flex-wrap:wrap;
      gap: 8px;
      margin-top: 14px;
    }

    .chip{
      display:inline-flex;
      align-items:center;
      gap: 8px;
      padding: 7px 10px;
      border-radius: 999px;
      border: 1px solid var(--line);
      background: color-mix(in srgb, var(--paper) 85%, transparent);
      color: var(--muted);
      font-size: 12px;
      font-family: var(--mono);
      white-space:nowrap;
    }

    .hero-cta{
      display:flex;
      gap: 10px;
      flex-wrap:wrap;
      margin-top: 14px;
    }

    /* System Map */
    .map{
      border-left: 1px solid var(--line);
      padding-left: 14px;
    }
    .map h3{
      margin: 0;
      font-size: 12px;
      color: var(--muted);
      font-family: var(--mono);
      letter-spacing: .5px;
      text-transform: uppercase;
    }

    .diagram{
      margin-top: 10px;
      border: 1px dashed var(--line2);
      border-radius: var(--radius);
      background:
        radial-gradient(240px 120px at 30% 25%, color-mix(in srgb, var(--accent) 10%, transparent), transparent 65%),
        radial-gradient(240px 120px at 75% 60%, color-mix(in srgb, var(--accent2) 10%, transparent), transparent 65%),
        color-mix(in srgb, var(--paper) 90%, transparent);
      padding: 14px;
      min-height: 220px;
      position: relative;
      overflow:hidden;
    }

    /* contour-ish lines */
    .diagram:before{
      content:"";
      position:absolute;
      inset:-30px;
      background:
        repeating-radial-gradient(circle at 20% 30%,
          transparent 0 12px,
          color-mix(in srgb, var(--line) 70%, transparent) 12px 13px),
        repeating-radial-gradient(circle at 80% 70%,
          transparent 0 14px,
          color-mix(in srgb, var(--line) 70%, transparent) 14px 15px);
      opacity: .35;
      pointer-events:none;
    }

    .node{
      position:absolute;
      border-radius: 14px;
      border: 1px solid var(--line2);
      background: color-mix(in srgb, var(--paper) 92%, transparent);
      padding: 10px 10px;
      box-shadow: var(--shadow2);
      min-width: 140px;
      transition: transform .14s ease, border-color .14s ease, background .14s ease;
      cursor: pointer;
      -webkit-user-select: none;
         -moz-user-select: none;
          -ms-user-select: none;
              user-select: none;
    }

    .node strong{
      display:block;
      font-size: 12px;
      letter-spacing: .1px;
    }
    .node span{
      display:block;
      margin-top: 4px;
      color: var(--muted);
      font-family: var(--mono);
      font-size: 11px;
    }

    .node.active{
      transform: translateY(-2px);
      border-color: color-mix(in srgb, var(--accent) 50%, var(--line2));
      background: color-mix(in srgb, var(--accent) 8%, var(--paper));
    }

    .node.n1{ left: 14px; top: 18px; }
    .node.n2{ right: 14px; top: 26px; }
    .node.n3{ left: 20px; bottom: 18px; }
    .node.n4{ right: 18px; bottom: 20px; }

    .wire{
      position:absolute;
      inset:0;
      pointer-events:none;
      opacity: .9;
    }

    /* Sections */
    section.block{
      scroll-margin-top: 86px;
    }

    .section-head{
      display:flex;
      align-items:flex-end;
      justify-content:space-between;
      gap: 12px;
      padding: 16px 18px;
      border-bottom: 1px solid var(--line);
      background: linear-gradient(180deg, color-mix(in srgb, var(--paper) 98%, transparent), transparent);
    }
    .section-head h2{
      margin:0;
      font-size: 16px;
      letter-spacing: -.2px;
    }
    .section-head p{
      margin:0;
      color: var(--muted);
      font-size: 13px;
      max-width: 68ch;
    }

    .cols{
      display:grid;
      grid-template-columns: 1fr 1fr;
      gap: 12px;
      padding: 14px 18px 18px;
    }

    .card{
      border: 1px solid var(--line);
      background: color-mix(in srgb, var(--paper) 94%, transparent);
      border-radius: var(--radius);
      padding: 14px;
      box-shadow: none;
      transition: transform .12s ease, border-color .12s ease, background .12s ease;
    }
    .card:hover{
      transform: translateY(-1px);
      border-color: color-mix(in srgb, var(--accent) 28%, var(--line2));
      background: color-mix(in srgb, var(--paper) 100%, transparent);
    }

    .card .label{
      font-family: var(--mono);
      font-size: 11px;
      color: var(--muted);
      text-transform: uppercase;
      letter-spacing: .6px;
    }
    .card h3{
      margin: 8px 0 6px;
      font-size: 14px;
    }
    .card p{
      margin:0;
      color: var(--muted);
      font-size: 13px;
    }
    .card .meta{
      margin-top: 10px;
      display:flex;
      gap: 8px;
      flex-wrap:wrap;
    }
    .pill{
      font-family: var(--mono);
      font-size: 11px;
      color: var(--faint);
      border: 1px solid var(--line);
      padding: 4px 8px;
      border-radius: 999px;
      background: color-mix(in srgb, var(--paper) 85%, transparent);
    }

    /* Footer */
    footer{
      margin-top: 10px;
      padding: 18px;
      display:flex;
      align-items:center;
      justify-content:space-between;
      gap: 12px;
      flex-wrap:wrap;
      border-top: 1px solid var(--line);
      color: var(--muted);
      font-size: 12px;
    }
    .foot-links{
      display:flex;
      gap: 12px;
      flex-wrap:wrap;
    }
    .foot-links a{
      color: var(--muted);
      border-bottom: 1px dotted transparent;
      padding-bottom: 2px;
    }
    .foot-links a:hover{
      color: var(--ink);
      border-bottom-color: color-mix(in srgb, var(--accent) 35%, transparent);
    }

    /* Responsive */
    @media (max-width: 980px){
      .layout{ grid-template-columns: 1fr; }
      .rail{ position: relative; top: 0; }
      .hero-top{ grid-template-columns: 1fr; }
      .map{ border-left: none; padding-left: 0; border-top: 1px solid var(--line); padding-top: 14px; }
      .cols{ grid-template-columns: 1fr; }
    }

    @media (prefers-reduced-motion: reduce){
      *{ transition:none !important; scroll-behavior:auto !important; }
    }