:root {
      --bg-color: white;
      --text-color: #1f2937;
      --button-bg: #e5e7eb;
      --button-hover-bg: #d1d5db;
      --display-bg: #f3f4f6;
      --display-text: #111827;
    }

    body.theme-light {
      --bg-color: white;
      --text-color: #1f2937;
      --button-bg: #e5e7eb;
      --button-hover-bg: #d1d5db;
      --display-bg: #f3f4f6;
      --display-text: #111827;
    }

    body.theme-dark {
      --bg-color: #1f2937;
      --text-color: #f3f4f6;
      --button-bg: #374151;
      --button-hover-bg: #4b5563;
      --display-bg: #111827;
      --display-text: #f3f4f6;
    }

    body.theme-blue {
      --bg-color: #e0f2ff;
      --text-color: #003366;
      --button-bg: #cceeff;
      --button-hover-bg: #99ddff;
      --display-bg: #b3e0ff;
      --display-text: #003366;
    }

    body {
      background-color: var(--bg-color);
      color: var(--text-color);
      transition: background-color 0.3s, color 0.3s;
    }

    .display {
      background-color: var(--display-bg);
      color: var(--display-text);
    }

    .calc-button {
      background-color: var(--button-bg);
      color: var(--text-color);
      transition: background-color 0.2s;
    }

    .calc-button:hover {
      background-color: var(--button-hover-bg);
    }

    table {
      width: 100%;
      border-collapse: collapse;
    }

    th,
    td {
      padding: 6px 8px;
      border-bottom: 1px solid #d1d5db;
      text-align: left;
    }

    tr:hover {
      background-color: rgba(0, 0, 0, 0.05);
    }

    td[contenteditable="true"] {
      cursor: text;
    }

    td[contenteditable="true"]:focus {
      outline: 2px solid #60a5fa;
      border-radius: 4px;
    }

    .delete-btn {
      color: #ef4444;
      cursor: pointer;
      font-weight: bold;
    }

    .delete-btn:hover {
      color: #b91c1c;
    }

    .undo-btn {
      color: #2563eb;
      cursor: pointer;
      text-decoration: underline;
    }

    .undo-btn:hover {
      color: #1d4ed8;
    }

    .export-btn {
      background-color: #10b981;
      color: white;
      padding: 4px 10px;
      border-radius: 6px;
      cursor: pointer;
    }

    .export-btn:hover {
      background-color: #059669;
    }

    #csvBtn {
      display: none;
    }