static String _computerID;
public static String computerID() ctex {
  if (_computerID == null) {
    File file = new File(userHome(), ".tinybrain/computer-id");
    _computerID = loadTextFile(file.getPath(), null);
    if (_computerID == null) {
      _computerID = makeRandomID(12);
      saveTextFile(file.getPath(), _computerID);
    }
  }
  return _computerID;
}