:root{
    --paper:#EFE6D3;
    --paper-dark:#E4D8BE;
    --plate:#FBF8F1;
    --ink:#1F3D2E;
    --ink-soft:#3C5A47;
    --ink-faint:#8A9A8E;
    --rust:#B5442E;
    --mustard:#C99A2E;
    --line:#C9BC9C;
    --line-strong:#1F3D2E;
    --ink-rgb:31,61,46;
    --rust-rgb:181,68,46;
    --mustard-rgb:201,154,46;
    --code-bg:#26443A;
    --code-label:#B9CFC0;
    --code-line:#3C5F51;
    --code-text:#CBD9CF;
    --code-ln:#5E7A6C;
    --code-active-text:#F7F0DA;
    --viz-done:#DCE7DA;
    --viz-dim:#F1EADA;
    --viz-found:#8FBF9F;
    --viz-start:#EAD9A8;
    --viz-fast:#E7C6B8;
  }
  html[data-theme="dark"]{
    --paper:#141F19;
    --paper-dark:#1B2A21;
    --plate:#0F1813;
    --ink:#D8E4D8;
    --ink-soft:#A8BCA9;
    --ink-faint:#6B7F70;
    --rust:#E06A4E;
    --mustard:#E0B14A;
    --line:#2E4034;
    --line-strong:#D8E4D8;
    --ink-rgb:216,228,216;
    --rust-rgb:224,106,78;
    --mustard-rgb:224,177,74;
    --code-bg:#0C1410;
    --code-label:#8FA795;
    --code-line:#2E4A3C;
    --code-text:#BED2C2;
    --code-ln:#55705F;
    --code-active-text:#F2EAD3;
    --viz-done:#2E4A38;
    --viz-dim:#20291F;
    --viz-found:#3F7A55;
    --viz-start:#6B5A2A;
    --viz-fast:#6E4638;
  }
  *{box-sizing:border-box;}
  html{scroll-behavior:smooth;}
  body{
    margin:0;
    background:var(--paper);
    color:var(--ink);
    font-family:'Spectral', serif;
    font-size:17px;
    line-height:1.6;
    background-image:
      radial-gradient(circle at 1px 1px, rgba(var(--ink-rgb),0.06) 1px, transparent 0);
    background-size:22px 22px;
  }
  ::selection{ background:var(--mustard); color:var(--ink);}
  a{color:var(--rust);}
  h1,h2,h3{ font-family:'Fraunces', serif; font-weight:600; margin:0; letter-spacing:-0.01em;}
  .mono{ font-family:'JetBrains Mono', monospace; }
  .wrap{ max-width:1040px; margin:0 auto; padding:0 28px; }

  :focus-visible{ outline:3px solid var(--rust); outline-offset:3px; }

  /* ---------- HERO ---------- */
  .hero{ padding:90px 0 60px; border-bottom:1px solid var(--line); position:relative; overflow:hidden; }
  .hero-rain{ position:absolute; inset:0; z-index:0; pointer-events:none; }
  .hero .wrap{ display:grid; grid-template-columns: 1.15fr 0.85fr; gap:48px; align-items:center; position:relative; z-index:1; }
  .eyebrow{
    font-family:'JetBrains Mono', monospace; font-size:12px; letter-spacing:0.14em;
    text-transform:uppercase; color:var(--rust); display:flex; align-items:center; gap:10px; margin-bottom:18px;
  }
  .eyebrow::before{ content:""; width:26px; height:1px; background:var(--rust); display:inline-block; }
  .hero h1{ font-size:clamp(38px,5.6vw,64px); line-height:1.02; }
  .hero h1 em{ font-style:italic; color:var(--ink-soft); }
  .hero p.lede{ margin-top:20px; max-width:46ch; color:var(--ink-soft); font-size:19px; }
  .hero .ctas{ margin-top:30px; display:flex; gap:14px; flex-wrap:wrap; }
  .btn{
    font-family:'JetBrains Mono', monospace; font-size:13px; letter-spacing:.03em;
    padding:12px 18px; border:1px solid var(--ink); background:transparent; color:var(--ink);
    cursor:pointer; text-decoration:none; display:inline-flex; align-items:center; gap:8px;
    transition:background .15s ease, color .15s ease;
  }
  .btn:hover{ background:var(--ink); color:var(--plate); }
  .btn.primary{ background:var(--ink); color:var(--plate); }
  .btn.primary:hover{ background:var(--rust); border-color:var(--rust); }

  .sound-toggle{
    position:fixed; top:18px; right:18px; z-index:50;
    font-family:'JetBrains Mono',monospace; font-size:12px; letter-spacing:.03em;
    padding:9px 14px; border:1px solid var(--ink); background:var(--plate); color:var(--ink);
    cursor:pointer; display:flex; align-items:center; gap:7px; box-shadow:0 2px 8px rgba(var(--ink-rgb),0.18);
  }
  .sound-toggle:hover{ background:var(--ink); color:var(--plate); }
  .theme-toggle{ right:104px; justify-content:center; }
  @media (max-width:600px){
    .sound-toggle{ top:auto; bottom:18px; right:18px; }
    .theme-toggle{ right:18px; bottom:66px; }
  }

  .hero-plate{
    background:var(--plate); border:1px solid var(--line-strong); position:relative; padding:18px;
  }
  .hero-viz-caption{
    margin-top:10px; font-family:'JetBrains Mono',monospace; font-size:11px; color:var(--ink-faint); text-align:left;
  }
  .hero-viz-caption b{ color:var(--rust); font-weight:500; }

  .scroll-cue{
    position:absolute; left:50%; bottom:14px; transform:translateX(-50%);
    display:flex; flex-direction:column; align-items:center; gap:5px; z-index:2;
    font-family:'JetBrains Mono',monospace; font-size:10px; letter-spacing:.12em; text-transform:uppercase;
    color:var(--ink-faint); text-decoration:none;
  }
  .scroll-cue:hover{ color:var(--rust); }
  .scroll-cue .chevron{ animation: scrollBounce 1.7s ease-in-out infinite; }
  @keyframes scrollBounce{ 0%,100%{ transform:translateY(0); opacity:.55; } 50%{ transform:translateY(7px); opacity:1; } }
  @media (max-width:820px){ .scroll-cue{ display:none; } }

  /* ---------- TOC ---------- */
  .toc{ padding:56px 0; border-bottom:1px solid var(--line); }
  .toc-head{ display:flex; justify-content:space-between; align-items:baseline; margin-bottom:26px; }
  .toc-head h2{ font-size:22px; }
  .toc-head span{ font-family:'JetBrains Mono',monospace; font-size:12px; color:var(--ink-faint); }
  .toc-grid{ display:grid; grid-template-columns:repeat(3,1fr); gap:1px; background:var(--line); border:1px solid var(--line); }
  .toc-card{
    background:var(--paper);
    padding:22px;
    border:1px solid transparent;
    transition:background .15s ease,
      transform .28s cubic-bezier(.34,1.56,.64,1),
      box-shadow .28s cubic-bezier(.34,1.56,.64,1),
      border-color .28s cubic-bezier(.34,1.56,.64,1);
  }
  .toc-card:hover, .toc-card:focus-within{
    background:var(--paper-dark);
    transform:translateY(-6px);
    box-shadow:0 8px 20px rgba(var(--rust-rgb),.18);
    border-color:var(--rust);
  }
  .toc-card-link{ display:block; text-decoration:none; color:var(--ink); }
  .toc-num{
    font-family:'JetBrains Mono',monospace;
    color:var(--rust);
    font-size:13px;
    display:inline-block;
    transition:transform .28s cubic-bezier(.34,1.56,.64,1),
      text-shadow .28s cubic-bezier(.34,1.56,.64,1),
      letter-spacing .28s cubic-bezier(.34,1.56,.64,1);
  }
  .toc-card:hover .toc-num, .toc-card:focus-within .toc-num{
    transform:scale(1.08);
    letter-spacing:.03em;
    text-shadow:0 1px 8px rgba(var(--rust-rgb),.35);
  }
  .toc-card.toc-anim{
    opacity:0;
    transform:translateY(24px);
    transition:opacity .42s cubic-bezier(.34,1.56,.64,1),
      transform .42s cubic-bezier(.34,1.56,.64,1);
  }
  .toc-card.toc-anim.toc-anim-visible{
    opacity:1;
    transform:translateY(0);
  }
  .toc-card h3{ font-size:20px; margin-top:8px; }
  .toc-card p{ margin:8px 0 0; font-size:14px; color:var(--ink-soft); }
  .toc-badge{
    font-family:'JetBrains Mono',monospace; font-size:10px; letter-spacing:.06em;
    color:var(--mustard); border:1px solid var(--mustard); padding:1px 6px;
    margin-left:10px; display:inline-block; vertical-align:2px;
  }
  .toc-head-meta{ display:inline-flex; align-items:baseline; gap:8px; }
  .toc-cheatsheet{
    font-family:'JetBrains Mono',monospace; font-size:12px; color:var(--rust);
    text-decoration:none; margin-left:8px;
  }
  .toc-cheatsheet:hover{ text-decoration:underline; }
  #toc-progress{ font-family:'JetBrains Mono',monospace; font-size:12px; color:var(--mustard); }
  .toc-learn-more{
    display:inline-flex; align-items:center; margin-top:14px;
    font-family:'JetBrains Mono',monospace; font-size:12px; letter-spacing:.03em;
    color:var(--rust); text-decoration:none;
  }
  .toc-learn-more:hover{ color:var(--ink); text-decoration:underline; }

  /* ---------- SPECIMEN SECTIONS ---------- */
  .specimen{ padding:78px 0; border-bottom:1px solid var(--line); }
  .specimen-tag{
    display:inline-flex; align-items:center; gap:8px; font-family:'JetBrains Mono',monospace;
    font-size:11px; letter-spacing:.12em; text-transform:uppercase; color:var(--plate);
    background:var(--ink); padding:5px 10px;
  }
  .specimen h2{ font-size:clamp(28px,4vw,42px); margin-top:16px; }
  .specimen h2 i{ color:var(--ink-faint); font-style:italic; font-size:0.55em; display:block; margin-top:6px; }
  .specimen .desc{ max-width:62ch; color:var(--ink-soft); margin-top:16px; }
  .specimen .btn.learn-more{ margin-top:22px; }

  .plate{
    background:var(--plate); border:1px solid var(--line-strong); margin-top:36px; position:relative;
  }
  .plate-label{
    position:absolute; top:-11px; left:20px; background:var(--paper); padding:0 8px;
    font-family:'JetBrains Mono',monospace; font-size:10px; letter-spacing:.1em; color:var(--ink-faint);
  }
  .plate-inner{ padding:28px; }
  .viz{ width:100%; height:auto; display:block; }

  .viz-code-grid{ display:grid; grid-template-columns:1.35fr 1fr; gap:26px; align-items:start; }
  /* grid items must not floor at the code's min-content width — long pseudocode
     lines otherwise force the column (and the page) wider than the viewport */
  .viz-code-grid > *{ min-width:0; }
  .code-col{ background:var(--code-bg); border:1px solid var(--ink); }
  .code-label{
    font-family:'JetBrains Mono',monospace; font-size:10px; letter-spacing:.1em; text-transform:uppercase;
    color:var(--code-label); padding:9px 14px; border-bottom:1px solid var(--code-line); display:flex; justify-content:space-between;
  }
  .code-label::after{ content:"● ● ●"; letter-spacing:2px; opacity:.5; font-size:8px; }
  .code-block{ margin:0; padding:14px 0; font-family:'JetBrains Mono',monospace; font-size:12.5px; line-height:1.9; overflow-x:auto; }
  .code-block .cl{ padding:1px 14px 1px 0; display:flex; white-space:pre; color:var(--code-text); transition:background .15s ease, color .15s ease; }
  .code-block .cl .ln{ width:28px; flex:none; text-align:right; margin-right:14px; color:var(--code-ln); user-select:none; }
  .code-block .cl.active{ background:var(--code-line); color:var(--code-active-text); }
  .code-block .cl.active .ln{ color:var(--mustard); }
  @media (max-width:900px){ .viz-code-grid{ grid-template-columns:1fr; } }

  .controls{
    display:flex; align-items:center; gap:10px; flex-wrap:wrap; padding:16px 28px;
    border-top:1px solid var(--line); background:var(--paper-dark);
  }
  .controls button{
    font-family:'JetBrains Mono',monospace; font-size:12px; border:1px solid var(--ink);
    background:var(--plate); color:var(--ink); padding:8px 14px; cursor:pointer;
  }
  .controls button:hover{ background:var(--ink); color:var(--plate); }
  .controls button:disabled{ opacity:.4; cursor:not-allowed; }
  .controls .spacer{ flex:1; }
  .controls label{ font-family:'JetBrains Mono',monospace; font-size:11px; color:var(--ink-soft); display:flex; align-items:center; gap:6px;}
  .controls input[type=range]{ accent-color:var(--rust); }

  .readout{
    margin-top:18px; display:grid; grid-template-columns:repeat(auto-fit,minmax(160px,1fr)); gap:1px;
    background:var(--line); border:1px solid var(--line);
  }
  .readout div{ background:var(--paper); padding:12px 16px; }
  .readout .k{ font-family:'JetBrains Mono',monospace; font-size:10px; letter-spacing:.08em; text-transform:uppercase; color:var(--ink-faint); }
  .readout .v{ font-family:'JetBrains Mono',monospace; font-size:15px; color:var(--ink); margin-top:4px; }

  .stepline{ margin-top:16px; font-family:'JetBrains Mono',monospace; font-size:13px; color:var(--ink-soft); min-height:20px; }
  .stepline b{ color:var(--rust); }

  .target-picker{ display:flex; gap:8px; flex-wrap:wrap; margin-top:14px; }
  .target-picker button{
    font-family:'JetBrains Mono',monospace; font-size:13px; border:1px solid var(--line-strong);
    background:var(--plate); padding:6px 12px; cursor:pointer; color:var(--ink);
  }
  .target-picker button.active{ background:var(--rust); border-color:var(--rust); color:var(--plate); }

  /* ---------- FIELD NOTES / FOOTER ---------- */
  .notes{ padding:70px 0 90px; }
  .notes h2{ font-size:26px; margin-bottom:26px; }
  table.idcard{ width:100%; border-collapse:collapse; font-family:'JetBrains Mono',monospace; font-size:13px; }
  table.idcard th, table.idcard td{ text-align:left; padding:12px 14px; border-bottom:1px solid var(--line); }
  table.idcard th{ color:var(--ink-faint); font-weight:500; text-transform:uppercase; letter-spacing:.06em; font-size:11px; }
  table.idcard td.spec{ font-family:'Spectral', serif; font-size:15px; color:var(--ink); }
  .resources{ margin-top:56px; }
  .resources-head{ margin-bottom:24px; }
  .resources-head h2{ font-size:24px; }
  .resources-head p{ margin:8px 0 0; color:var(--ink-soft); font-size:15px; max-width:60ch; }
  .res-grid{ display:grid; grid-template-columns:repeat(3,1fr); gap:1px; background:var(--line); border:1px solid var(--line); }
  .res-col{ background:var(--paper); padding:22px 22px 26px; }
  .res-col h3{
    font-family:'JetBrains Mono',monospace; font-size:11px; letter-spacing:.1em; text-transform:uppercase;
    color:var(--rust); margin-bottom:16px; padding-bottom:10px; border-bottom:1px solid var(--line);
  }
  .res-col ul{ list-style:none; margin:0; padding:0; }
  .res-col li{ margin-bottom:16px; }
  .res-col li:last-child{ margin-bottom:0; }
  .res-col a{
    text-decoration:none; color:var(--ink); font-family:'Fraunces',serif; font-size:17px; font-weight:600;
    display:inline-flex; align-items:center; gap:6px;
  }
  .res-col a:hover{ color:var(--rust); }
  .res-col a .ext{ font-family:'JetBrains Mono',monospace; font-size:11px; color:var(--ink-faint); font-weight:400; }
  .res-col a:hover .ext{ color:var(--rust); }
  .res-col .res-note{ display:block; margin-top:3px; font-size:13px; color:var(--ink-soft); font-family:'Spectral',serif; }
  @media (max-width:820px){ .res-grid{ grid-template-columns:1fr; } }

  .foot{ margin-top:60px; padding-top:24px; border-top:1px solid var(--line); font-family:'JetBrains Mono',monospace; font-size:12px; color:var(--ink-faint); display:flex; justify-content:space-between; flex-wrap:wrap; gap:10px; }

  /* ---------- per-specimen "practice on LeetCode" row ---------- */
  .practice{
    margin-top:20px; display:flex; align-items:center; flex-wrap:wrap; gap:12px;
    padding:16px 18px; background:var(--plate); border:1px solid var(--line);
  }
  .practice-label{
    font-family:'JetBrains Mono',monospace; font-size:11px; letter-spacing:.08em; text-transform:uppercase;
    color:var(--rust); display:inline-flex; align-items:center; gap:8px; margin-right:2px;
  }
  .practice-label::before{ content:"→"; }
  .practice-links{ display:flex; flex-wrap:wrap; gap:8px; }
  .practice-links a{
    font-family:'JetBrains Mono',monospace; font-size:12.5px; text-decoration:none;
    color:var(--ink); border:1px solid var(--line-strong); padding:6px 11px;
    display:inline-flex; align-items:center; gap:6px; transition:background .14s ease, color .14s ease;
  }
  .practice-links a:hover{ background:var(--ink); color:var(--plate); }
  .practice-links a .lc-dot{ width:6px; height:6px; border-radius:50%; background:var(--mustard); flex:none; }
  .practice-links a:hover .lc-dot{ background:var(--plate); }

  /* ---------- footer social links ---------- */
  .socials{ display:flex; align-items:center; gap:14px; flex-wrap:wrap; }
  .foot{ align-items:center; }
  .socials .socials-label{ font-family:'JetBrains Mono',monospace; font-size:11px; letter-spacing:.08em; text-transform:uppercase; color:var(--ink-faint); margin-right:4px; }
  .socials a{
    width:40px; height:40px; border:1px solid var(--line-strong); display:inline-flex; align-items:center; justify-content:center;
    color:var(--ink); transition:background .14s ease, color .14s ease, transform .14s ease;
  }
  .socials a:hover{ background:var(--ink); color:var(--plate); transform:translateY(-2px); }
  .socials a svg{ width:19px; height:19px; display:block; }

  @media (max-width:820px){
    .hero .wrap{ grid-template-columns:1fr; }
    .toc-grid{ grid-template-columns:1fr; }
    table.idcard{ display:block; overflow-x:auto; }
  }
  @media (prefers-reduced-motion: reduce){
    *{ transition:none !important; animation:none !important; scroll-behavior:auto !important; }
    .toc-card:hover, .toc-card:focus-within{
      transform:none;
      box-shadow:none;
      border-color:transparent;
    }
    .toc-card:hover .toc-num, .toc-card:focus-within .toc-num{
      transform:none;
      text-shadow:none;
      letter-spacing:normal;
    }
  }

  /* bar/svg element helpers */
  .bar-label{ font-family:'JetBrains Mono',monospace; font-size:11px; fill:var(--ink-soft); }
  .leader{ stroke:var(--ink-faint); stroke-width:1; stroke-dasharray:2 3; }