:root{
    --bg:#EEF1F5;
    --paper:#FFFFFF;
    --paper-2:#F4F7FA;
    --ink:#182430;
    --muted:#5B6B7C;
    --accent:#A9761E;
    --accent-ink:#FFFFFF;
    --blue:#2B5C8A;
    --good:#2F7A4F;
    --good-ink:#F2FBF5;
    --bad:#B5453D;
    --border:#D7DEE6;
    --grid-line: rgba(43,92,138,0.10);
    --focus:#2B5C8A;
  }
  @media (prefers-color-scheme: dark){
    :root:not([data-theme="light"]){
      --bg:#10151C;
      --paper:#161D27;
      --paper-2:#1C2530;
      --ink:#E9EEF3;
      --muted:#93A3B4;
      --accent:#D8A64B;
      --accent-ink:#221800;
      --blue:#7FB2DE;
      --good:#5FBE84;
      --good-ink:#062011;
      --bad:#E2857D;
      --border:#2A3542;
      --grid-line: rgba(127,178,222,0.09);
      --focus:#D8A64B;
    }
  }
  :root[data-theme="dark"]{
    --bg:#10151C;
    --paper:#161D27;
    --paper-2:#1C2530;
    --ink:#E9EEF3;
    --muted:#93A3B4;
    --accent:#D8A64B;
    --accent-ink:#221800;
    --blue:#7FB2DE;
    --good:#5FBE84;
    --good-ink:#062011;
    --bad:#E2857D;
    --border:#2A3542;
    --grid-line: rgba(127,178,222,0.09);
    --focus:#D8A64B;
  }

  *{box-sizing:border-box;}
  body{
    margin:0;
    font-family:'Work Sans',system-ui,-apple-system,Segoe UI,sans-serif;
    color:var(--ink);
    background-color:var(--bg);
    background-image:
      repeating-linear-gradient(0deg, var(--grid-line) 0 1px, transparent 1px 28px),
      repeating-linear-gradient(90deg, var(--grid-line) 0 1px, transparent 1px 28px);
    min-height:100vh;
    padding-bottom:70px;
  }
  @media (prefers-reduced-motion: reduce){
    *{transition:none !important; animation:none !important;}
  }

  a{color:var(--blue);}
  :focus-visible{outline:3px solid var(--focus); outline-offset:2px;}

  header{
    text-align:center;
    padding:44px 20px 22px;
  }
  .kicker{
    font-family:'IBM Plex Mono',monospace;
    font-size:.72rem;
    letter-spacing:.14em;
    text-transform:uppercase;
    color:var(--muted);
    margin:0 0 10px;
  }
  header h1{
    font-family:'Special Elite',ui-monospace,monospace;
    font-weight:400;
    font-size:2.3rem;
    margin:0 0 8px;
    letter-spacing:0.5px;
    text-wrap:balance;
  }
  header p.sub{
    color:var(--muted);
    margin:0;
    font-size:1.05rem;
  }

  .wrap{
    max-width:800px;
    margin:0 auto;
    padding:0 18px;
  }

  .intro{
    background:var(--paper);
    border:1px solid var(--border);
    border-radius:4px;
    border-left:4px solid var(--accent);
    padding:20px 24px;
    margin:22px 0;
  }
  .intro h2{
    margin-top:0;
    font-family:'IBM Plex Mono',monospace;
    font-size:.85rem;
    letter-spacing:.08em;
    text-transform:uppercase;
    color:var(--accent);
  }
  .intro ul{margin:10px 0 0;padding-left:20px;color:var(--ink);line-height:1.7;}
  .intro li{margin-bottom:4px;}
  .intro strong{color:var(--blue);}

  .top-bar{
    display:flex;
    align-items:center;
    justify-content:space-between;
    gap:16px;
    flex-wrap:wrap;
    background:var(--paper);
    border:1px solid var(--border);
    border-radius:4px;
    padding:14px 20px;
    margin:22px 0;
    position:sticky;
    top:10px;
    z-index:10;
    box-shadow:0 6px 18px rgba(24,36,48,0.12);
  }
  .timer{
    font-family:'IBM Plex Mono',monospace;
    font-variant-numeric:tabular-nums;
    font-size:1.25rem;
    font-weight:600;
    color:var(--accent);
  }
  .progress-track{
    flex:1;
    min-width:160px;
    height:10px;
    background:var(--paper-2);
    border-radius:5px;
    overflow:hidden;
    border:1px solid var(--border);
  }
  .progress-fill{
    height:100%;
    width:0%;
    background:var(--accent);
    transition:width .4s ease;
  }
  .vault-letters{
    display:flex;
    gap:6px;
    font-family:'IBM Plex Mono',monospace;
  }
  .letter-slot{
    width:30px;height:34px;
    border-radius:3px;
    background:var(--paper-2);
    border:1px solid var(--border);
    display:flex;align-items:center;justify-content:center;
    font-weight:600;
    color:var(--muted);
  }
  .letter-slot.filled{
    background:var(--good);
    color:var(--good-ink);
    border-color:var(--good);
  }

  .station{
    background:var(--paper);
    border:1px solid var(--border);
    border-radius:4px;
    margin:16px 0;
    overflow:hidden;
  }
  .station-head{
    display:flex;
    align-items:center;
    justify-content:space-between;
    gap:12px;
    padding:16px 20px;
    cursor:pointer;
    user-select:none;
  }
  .station-head h3{
    margin:0;
    font-size:1.02rem;
    font-weight:600;
    display:flex;
    align-items:center;
    gap:10px;
  }
  .lock-icon{font-size:1.2rem;}
  .station-badge{
    font-family:'IBM Plex Mono',monospace;
    font-size:.72rem;
    padding:3px 10px;
    border-radius:20px;
    background:var(--paper-2);
    color:var(--muted);
    border:1px solid var(--border);
    white-space:nowrap;
  }
  .station.solved .station-badge{
    background:var(--good);
    color:var(--good-ink);
    border-color:var(--good);
  }
  .station-body{
    padding:0 20px 20px;
    display:block;
    border-top:1px solid var(--border);
  }
  .station-body.collapsed{display:none;}
  .question{
    background:var(--paper-2);
    border:1px solid var(--border);
    border-radius:4px;
    padding:14px 16px;
    margin:14px 0 0;
  }
  .question p{margin:0 0 10px;font-size:1.02rem;line-height:1.5;}
  .answer-row{
    display:flex;
    gap:8px;
    flex-wrap:wrap;
    align-items:center;
  }
  input[type=text]{
    flex:1;
    min-width:140px;
    padding:9px 12px;
    border-radius:4px;
    border:1px solid var(--border);
    background:var(--paper);
    color:var(--ink);
    font-family:'IBM Plex Mono',monospace;
    font-size:.98rem;
  }
  button{
    padding:9px 16px;
    border-radius:4px;
    border:1px solid var(--accent);
    background:var(--accent);
    color:var(--accent-ink);
    font-weight:600;
    cursor:pointer;
    font-size:.92rem;
    font-family:'Work Sans',sans-serif;
  }
  button.secondary{
    background:transparent;
    color:var(--muted);
    border:1px solid var(--border);
  }
  input:disabled, button:disabled{
    opacity:.4;
    cursor:not-allowed;
  }
  .feedback{
    margin-top:8px;
    font-size:.9rem;
    min-height:18px;
    font-weight:500;
  }
  .feedback.correct{color:var(--good);}
  .feedback.wrong{color:var(--bad);}
  .hint-text{
    margin-top:8px;
    font-size:.87rem;
    color:var(--blue);
    display:none;
  }
  .station-unlock-msg{
    display:none;
    margin-top:12px;
    padding:10px 14px;
    background:var(--paper);
    border:1px solid var(--good);
    border-left:4px solid var(--good);
    border-radius:4px;
    color:var(--good);
    font-weight:600;
    font-size:.92rem;
  }

  .vault-panel{
    background:var(--paper);
    border:1px solid var(--border);
    border-top:4px solid var(--accent);
    border-radius:4px;
    padding:24px;
    margin:26px 0;
    text-align:center;
    transition:border-color .3s ease;
  }
  .vault-panel.unlocked{
    border-top-color:var(--good);
  }
  .vault-panel h2{
    margin-top:0;
    font-family:'Special Elite',ui-monospace,monospace;
    font-weight:400;
    font-size:1.4rem;
    color:var(--ink);
  }
  #vaultStatusMsg{color:var(--muted);font-size:.95rem;}
  .vault-panel.unlocked #vaultStatusMsg{color:var(--good);font-weight:600;}
  .vault-input-row{
    display:flex;
    gap:10px;
    justify-content:center;
    margin-top:14px;
    flex-wrap:wrap;
  }
  .vault-input-row input{
    max-width:220px;
    text-align:center;
    text-transform:uppercase;
    letter-spacing:4px;
    font-weight:600;
  }

  .success-screen{
    display:none;
    text-align:center;
    padding:32px 20px;
    background:var(--paper);
    border:1px solid var(--good);
    border-top:4px solid var(--good);
    border-radius:4px;
    margin:22px 0;
  }
  .success-screen h2{
    font-family:'Special Elite',ui-monospace,monospace;
    font-weight:400;
    font-size:1.7rem;
    margin-bottom:8px;
    color:var(--good);
  }
  .success-screen p{color:var(--muted);}

  footer{
    text-align:center;
    color:var(--muted);
    font-size:.8rem;
    margin-top:34px;
    font-family:'IBM Plex Mono',monospace;
  }

  @media (max-width:520px){
    .top-bar{flex-direction:column;align-items:stretch;}
    .vault-letters{justify-content:center;}
  }