anchor.diff:      // Create button.
       button = new fl.Button(half, 0, width - half, 40, 'Recompile!');
       button.box = fl.FLAT_BOX;
  +    button.color = fl.WHITE;
       button.labelsize = 20;
  -    button.color = fl.DARK2;
       button.callback = (w, _) {
         update();
       };
  
positive.code: 
    void update() {
      button.labelfont = fl.COURIER;
      button.labeltype = fl.NORMAL_LABEL;
      button.labelcolor = fl.BLACK;
      button.label = 'Recompile';
      button.redraw();
  
negative.code:   Creal = real;
    Cimag = imag;
  
    for (iter = 0; iter < iterations; iter++) {
      // z = z^2 + c
      tempreal = real;
      tempimag = imag;
  