code: def zoom(params, factor):
      
      params.zoom /= factor
  
      n_x = params.mb_cx / params.zoom
      n_y = params.mb_cy / params.zoom
  
      params.plane_x0 = int((n_x + 1.0) * params.plane_w / (2.0 * params.plane_ratio)) - params.plane_w // 2
      params.plane_y0 = int((n_y + 1.0) * params.plane_h / 2.0) - params.plane_h // 2
docs: Applies a zoom on the current parameters.
  
      Computes the top-left plane-space coordinates from the Mandelbrot-space coordinates.
  
      :param params: Current application parameters.
      :param factor: Zoom factor by which the zoom ratio is divided (bigger factor, more zoom)