:root {
      --bg-color: #f8fafc;
      --card-bg: #ffffff;
      --text-main: #0f172a;
      --text-muted: #64748b;
      --border-color: #cbd5e1;
      --primary-color: #2563eb;
      --primary-hover: #1d4ed8;
      --accent-color: #10b981;
      --nav-bg: #1e293b;
      --nav-text: #f8fafc;
      --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
      --radius: 10px;
    }

    [data-theme="dark"] {
      --bg-color: #0f172a;
      --card-bg: #1e293b;
      --text-main: #f8fafc;
      --text-muted: #94a3b8;
      --border-color: #334155;
      --primary-color: #3b82f6;
      --primary-hover: #60a5fa;
      --accent-color: #34d399;
      --nav-bg: #020617;
      --nav-text: #f8fafc;
    }

    * { box-sizing: border-box; margin: 0; padding: 0; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif; }
    body { background-color: var(--bg-color); color: var(--text-main); min-height: 100vh; display: flex; flex-direction: column; transition: background-color 0.3s, color 0.3s; }

    header {
      background-color: var(--nav-bg);
      color: var(--nav-text);
      padding: 1rem 2rem;
      display: flex;
      justify-content: space-between;
      align-items: center;
      box-shadow: var(--shadow);
    }
    header h1 { font-size: 1.4rem; font-weight: 700; }

    .theme-toggle {
      background: transparent;
      border: 1px solid var(--border-color);
      color: var(--nav-text);
      padding: 0.4rem 0.8rem;
      border-radius: var(--radius);
      cursor: pointer;
      font-size: 0.85rem;
    }

    .cat-nav {
      display: flex;
      background: var(--card-bg);
      border-bottom: 1px solid var(--border-color);
      overflow-x: auto;
    }
    .cat-btn {
      padding: 1rem 1.5rem;
      background: transparent;
      border: none;
      border-bottom: 3px solid transparent;
      color: var(--text-muted);
      font-weight: 600;
      cursor: pointer;
      white-space: nowrap;
    }
    .cat-btn.active { color: var(--primary-color); border-bottom-color: var(--primary-color); }

    .main-container {
      display: grid;
      grid-template-columns: 280px 1fr;
      flex: 1;
    }
    @media (max-width: 800px) {
      .main-container { grid-template-columns: 1fr; }
    }

    .calc-sidebar {
      background-color: var(--card-bg);
      border-right: 1px solid var(--border-color);
      padding: 1rem;
      overflow-y: auto;
      max-height: calc(100vh - 120px);
    }
    .calc-btn {
      width: 100%;
      text-align: left;
      padding: 0.75rem 1rem;
      margin-bottom: 0.4rem;
      border: 1px solid transparent;
      background: transparent;
      color: var(--text-main);
      border-radius: var(--radius);
      cursor: pointer;
      font-weight: 500;
      font-size: 0.9rem;
      transition: background 0.2s;
    }
    .calc-btn:hover { background-color: var(--bg-color); }
    .calc-btn.active { background-color: var(--primary-color); color: #fff; }

    .calc-workspace { padding: 2rem; display: flex; justify-content: center; align-items: flex-start; }
    .calc-card {
      background: var(--card-bg);
      border: 1px solid var(--border-color);
      border-radius: var(--radius);
      padding: 1.5rem;
      width: 100%;
      max-width: 700px;
      box-shadow: var(--shadow);
      display: none;
    }
    .calc-card.active { display: block; }
    .calc-card h2 { margin-bottom: 1rem; font-size: 1.25rem; color: var(--primary-color); border-bottom: 1px solid var(--border-color); padding-bottom: 0.5rem; }

    .form-group { margin-bottom: 1rem; }
    .form-row { display: flex; gap: 10px; margin-bottom: 1rem; align-items: center; }
    .form-row > div { flex: 1; }
    label { display: block; font-size: 0.85rem; font-weight: 600; margin-bottom: 0.3rem; color: var(--text-muted); }
    input, select, textarea {
      width: 100%;
      padding: 0.6rem 0.8rem;
      border: 1px solid var(--border-color);
      border-radius: 6px;
      background-color: var(--bg-color);
      color: var(--text-main);
      font-size: 0.95rem;
      outline: none;
    }
    input:focus, select:focus { border-color: var(--primary-color); }

    .result-box {
      margin-top: 1.5rem;
      padding: 1rem;
      background-color: var(--bg-color);
      border-radius: var(--radius);
      border: 1px solid var(--border-color);
    }
    .result-item { display: flex; justify-content: space-between; margin-bottom: 0.5rem; font-size: 0.95rem; }
    .result-item:last-child { margin-bottom: 0; }
    .result-value { font-weight: 700; color: var(--accent-color); }
    .result-item.total .result-value { color: var(--primary-color); font-size: 1.1rem; }
    .disclaimer { font-size: 0.78rem; color: var(--text-muted); margin-top: 0.85rem; line-height: 1.4; border-top: 1px dashed var(--border-color); padding-top: 0.6rem; }

    .grid-buttons { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; margin-top: 10px; }
    .grid-buttons button { padding: 12px; font-size: 1.1rem; font-weight: 600; border-radius: 6px; border: 1px solid var(--border-color); background: var(--card-bg); color: var(--text-main); cursor: pointer; }
    .grid-buttons button:hover { background: var(--primary-color); color: #fff; }

    .canvas-container { margin-top: 1rem; text-align: center; }
    canvas { border: 1px solid var(--border-color); border-radius: 6px; background-color: #ffffff; max-width: 100%; }
    .fn-input-group { display: flex; gap: 8px; align-items: center; margin-bottom: 8px; }
    .fn-indicator { width: 14px; height: 14px; border-radius: 50%; display: inline-block; flex-shrink: 0; }