:root {
      --ink: #16202d;
      --sub: #546170;
      --line: rgba(22, 32, 45, 0.12);
      --card: rgba(255, 251, 245, 0.92);
      --card-strong: #fffdfa;
      --accent: #1f6fb2;
      --accent2: #b25733;
      --shadow: 0 24px 60px rgba(22, 58, 100, 0.12);
      --radius: 24px;
    }

    * { box-sizing: border-box; }

    body {
      margin: 0;
      color: var(--ink);
      font-family: "Source Han Sans SC", "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
      background:
        radial-gradient(circle at top right, rgba(92, 150, 210, 0.18), transparent 24%),
        radial-gradient(circle at left top, rgba(31, 111, 178, 0.12), transparent 20%),
        linear-gradient(180deg, #eef4fb 0%, #e4edf8 100%);
      min-height: 100vh;
    }

    .shell {
      width: min(1400px, calc(100vw - 32px));
      margin: 0 auto;
      padding: 20px 0 32px;
    }

    .topbar {
      display: flex;
      align-items: center;
      padding: 12px 22px;
      border-radius: 999px;
      border: 1px solid rgba(255, 255, 255, 0.6);
      background: rgba(240, 248, 255, 0.85);
      backdrop-filter: blur(10px);
      box-shadow: 0 12px 32px rgba(22, 58, 100, 0.08);
    }
    .topbar a {
      text-decoration: none;
      color: var(--accent);
      font-size: 16px;
      font-weight: 800;
    }

    .panel {
      margin-top: 14px;
      padding: 24px 28px;
      border-radius: var(--radius);
      border: 1px solid rgba(255, 255, 255, 0.55);
      background: var(--card);
      box-shadow: var(--shadow);
      backdrop-filter: blur(10px);
    }

    .hero {
      text-align: center;
      padding: 6px 0 16px;
    }
    .hero h1 {
      margin: 0;
      font-size: clamp(30px, 4vw, 46px);
      letter-spacing: 0.06em;
      color: var(--accent);
    }

    .layout {
      display: grid;
      grid-template-columns: 340px 1fr;
      gap: 18px;
      margin-top: 10px;
    }

    .card {
      border-radius: 20px;
      border: 1px solid var(--line);
      background: var(--card-strong);
      padding: 16px;
    }

    .controls h2,
    .chart h2 {
      margin: 0 0 10px;
      font-size: 22px;
      color: var(--ink);
    }

    .slider-group {
      margin-top: 10px;
      padding: 10px 12px;
      border-radius: 14px;
      background: #f6faff;
      border: 1px solid rgba(31, 111, 178, 0.16);
    }
    .slider-group label {
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-size: 17px;
      font-weight: 800;
      margin-bottom: 8px;
    }
    .slider-group .v {
      color: var(--accent);
      font-size: 20px;
      font-weight: 900;
      min-width: 64px;
      text-align: right;
    }
    .slider-group input[type="range"] {
      width: 100%;
      accent-color: var(--accent);
      cursor: pointer;
    }

    .formula {
      margin-top: 12px;
      border-radius: 14px;
      background: #fff8f2;
      border: 1px solid rgba(178, 87, 51, 0.2);
      padding: 12px;
      color: #7c3b20;
      line-height: 1.5;
    }
    .formula .eq-title {
      font-size: 16px;
      font-weight: 800;
      color: #8b4a2a;
      margin-bottom: 4px;
    }
    .formula .eq-main {
      margin-top: 4px;
    }
    .formula math {
      font-size: 30px;
      font-weight: 900;
      color: #7c3b20;
    }
    .formula .eq-sub {
      margin-top: 8px;
      padding-top: 6px;
      border-top: 1px dashed rgba(178, 87, 51, 0.28);
    }
    .formula .eq-sub math {
      font-size: 25px;
      font-weight: 800;
    }

    .stats {
      display: flex;
      gap: 10px;
      margin-top: 12px;
      flex-wrap: wrap;
    }
    .stat {
      flex: 1 1 96px;
      border-radius: 12px;
      border: 1px solid rgba(31, 111, 178, 0.15);
      background: #f3f9ff;
      padding: 8px 10px;
    }
    .stat .k {
      font-size: 13px;
      color: var(--sub);
      font-weight: 700;
    }
    .stat .val {
      margin-top: 3px;
      font-size: 18px;
      font-weight: 900;
      color: var(--accent);
    }

    .canvas-wrap {
      border-radius: 16px;
      border: 1px solid var(--line);
      background: #ffffff;
      padding: 10px;
      min-height: 480px;
      position: relative;
    }

    .canvas-wrap canvas {
      width: 100% !important;
      display: block;
    }

    .tip {
      margin-top: 10px;
      border-radius: 14px;
      background: linear-gradient(135deg, rgba(31, 111, 178, 0.08) 0%, rgba(92, 150, 210, 0.12) 100%);
      border: 1px solid rgba(31, 111, 178, 0.2);
      padding: 12px;
      font-size: 18px;
      font-weight: 800;
      line-height: 1.5;
    }

    @media (max-width: 980px) {
      .layout {
        grid-template-columns: 1fr;
      }
    }