:root{
      --bg:#0b1020;
      --panel:#0f1733;
      --text:#e9eeff;
      --muted:#9fb0ff;
      --shadow: 0 10px 30px rgba(0,0,0,.35);
      --gap: 14px;
      --matchW: 14px;
      --matchL: 68px;
      --matchT: 14px;
      --radius: 12px;
    }
    *{box-sizing:border-box}
    body{
      margin:0;
      min-height:100vh;
      background: radial-gradient(1200px 600px at 20% 20%, #1a2a7a 0%, transparent 60%),
                  radial-gradient(900px 500px at 85% 30%, #2b1a7a 0%, transparent 60%),
                  var(--bg);
      color:var(--text);
      font-family: system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, sans-serif;
      display:flex;
      align-items:center;
      justify-content:center;
      padding:24px;
    }
    .app{
      width:min(1100px, 100%);
      display:grid;
      grid-template-columns: 1.3fr .9fr;
      gap:18px;
    }
    @media (max-width: 980px){
      .app{grid-template-columns:1fr}
    }

    .card{
      background: linear-gradient(180deg, rgba(255,255,255,.06), rgba(255,255,255,.03));
      border: 1px solid rgba(255,255,255,.10);
      border-radius: 18px;
      box-shadow: var(--shadow);
      overflow:hidden;
    }
    .card-header{
      padding:16px 18px;
      border-bottom: 1px solid rgba(255,255,255,.10);
      display:flex;
      align-items:center;
      justify-content:space-between;
      gap:12px;
    }
    .title{
      display:flex;
      flex-direction:column;
      gap:4px;
    }
    .title h1{
      font-size:18px;
      margin:0;
      letter-spacing:.2px;
    }
    .title .sub{
      font-size:12px;
      color:var(--muted);
    }
    .controls{
      display:flex;
      gap:10px;
      flex-wrap:wrap;
      justify-content:flex-end;
    }
    button{
      border:none;
      padding:10px 12px;
      border-radius: 12px;
      background: rgba(255,255,255,.12);
      color:var(--text);
      cursor:pointer;
      font-weight:600;
      letter-spacing:.2px;
      transition: transform .05s ease, background .2s ease;
      user-select:none;
    }
    button:hover{ background: rgba(255,255,255,.18); }
    button:active{ transform: translateY(1px); }
    button.primary{
      background: linear-gradient(180deg, rgba(102,168,255,.7), rgba(102,168,255,.35));
    }
    button.primary:hover{
      background: linear-gradient(180deg, rgba(102,168,255,.85), rgba(102,168,255,.45));
    }

    .play{
      padding:18px;
      display:flex;
      flex-direction:column;
      gap:14px;
    }

    .statusRow{
      display:flex;
      flex-wrap:wrap;
      gap:10px;
      align-items:center;
      justify-content:space-between;
      background: rgba(0,0,0,.18);
      border: 1px solid rgba(255,255,255,.08);
      border-radius: 14px;
      padding:12px 14px;
    }
    .pill{
      display:inline-flex;
      align-items:center;
      gap:8px;
      padding:8px 10px;
      border-radius: 999px;
      background: rgba(255,255,255,.08);
      font-size:12px;
      color:var(--text);
      border:1px solid rgba(255,255,255,.08);
      white-space:nowrap;
    }
    .dot{
      width:10px;height:10px;border-radius:50%;
      background:#ff5c5c;
      box-shadow: 0 0 0 3px rgba(255,92,92,.15);
    }
    .dot.ok{
      background:#29e07a;
      box-shadow: 0 0 0 3px rgba(41,224,122,.15);
    }

    /* Equation layout */
    .equationWrap{
      background: rgba(0,0,0,.18);
      border: 1px solid rgba(255,255,255,.08);
      border-radius: 16px;
      padding:16px;
      overflow:auto;
    }
    .equation{
      display:flex;
      align-items:center;
      gap: var(--gap);
      padding:8px;
      min-width: 740px;
    }
    .group{
      display:flex;
      align-items:center;
      gap: var(--gap);
    }
    .symbol{
      font-size: 34px;
      font-weight: 900;
      color: rgba(255,255,255,.85);
      padding: 6px 10px;
      border-radius: 14px;
      background: rgba(255,255,255,.06);
      border: 1px solid rgba(255,255,255,.08);
      user-select:none;
    }

    /* 7-seg digit container */
    .digit{
      position:relative;
      width: 110px;
      height: 170px;
      border-radius: 16px;
      background: rgba(255,255,255,.04);
      border: 1px solid rgba(255,255,255,.07);
      box-shadow: inset 0 0 0 1px rgba(0,0,0,.35);
      flex:0 0 auto;
    }

    /* Match segments */
    .seg{
      position:absolute;
      width: var(--matchL);
      height: var(--matchW);
      border-radius: 999px;
      cursor:pointer;
      transition: filter .12s ease, transform .05s ease;
      box-shadow: 0 10px 18px rgba(0,0,0,.25);
    }
    .seg:hover{ filter: brightness(1.1); }
    .seg:active{ transform: translateY(1px); }

    /* removed (invisible/white) */
    .seg.removed{
      background: rgba(255,255,255,0) !important;
      box-shadow:none;
      cursor:not-allowed;
      pointer-events:none;
    }

    /* segment positions */
    /* a (top) */
    .seg.a{ top: 16px; left: 21px; }
    /* b (top-right) */
    .seg.b{ top: 32px; left: 73px; width: var(--matchW); height: var(--matchL); }
    /* c (bottom-right) */
    .seg.c{ top: 92px; left: 73px; width: var(--matchW); height: var(--matchL); }
    /* d (bottom) */
    .seg.d{ top: 146px; left: 21px; }
    /* e (bottom-left) */
    .seg.e{ top: 92px; left: 23px; width: var(--matchW); height: var(--matchL); }
    /* f (top-left) */
    .seg.f{ top: 32px; left: 23px; width: var(--matchW); height: var(--matchL); }
    /* g (middle) */
    .seg.g{ top: 81px; left: 21px; }

    .side{
      padding:18px;
      display:flex;
      flex-direction:column;
      gap:14px;
    }
    .hint{
      background: rgba(0,0,0,.18);
      border: 1px solid rgba(255,255,255,.08);
      border-radius: 16px;
      padding:14px;
      color: rgba(255,255,255,.9);
      font-size:13px;
      line-height:1.4;
    }
    .hint b{ color:#fff; }

    .removedBox{
      background: rgba(0,0,0,.18);
      border: 1px solid rgba(255,255,255,.08);
      border-radius: 16px;
      padding:14px;
      min-height: 160px;
      display:flex;
      flex-direction:column;
      gap:10px;
    }
    .removedHeader{
      display:flex;
      align-items:center;
      justify-content:space-between;
      gap:10px;
    }
    .removedHeader .label{
      font-weight:800;
      font-size:13px;
      color: rgba(255,255,255,.92);
    }
    .removedHeader .count{
      font-size:12px;
      color: var(--muted);
      white-space:nowrap;
    }
    .removedGrid{
      display:flex;
      flex-wrap:wrap;
      gap:10px;
      align-items:center;
    }
    .removedSeg{
      width: 44px;
      height: 16px;
      border-radius: 999px;
      box-shadow: 0 8px 16px rgba(0,0,0,.25);
      border: 1px solid rgba(255,255,255,.12);
    }
    .footerNote{
      font-size:12px;
      color: rgba(255,255,255,.7);
      line-height:1.35;
    }
    .mono{
      font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono","Courier New", monospace;
    }