public void start(Stage stage) {
    stage.setTitle("Dots!");
    // TODO: Your code starts here
    currentColor = Color.RED;
    dotList = new SinglyLinkedList<Dot>();
    Pane pane = new Pane();
    pane.setPrefSize(SIZE, SIZE);
    Dot dot = new Dot(50 ,50);
    dot.setFill(currentColor);
    //dotList.add(dot);
    //pane.getChildren().add(dot);
    Scene scene = new Scene(pane);
    stage.setScene(scene); // Place the scene in the stage

    pane.setOnKeyPressed(e -> {
        switch (e.getCode()) {
          case DIGIT1: currentColor = Color.RED; break;
          case DIGIT2:  currentColor = Color.BLUE; break;
          case DIGIT3: currentColor = Color.GREEN; break;
          case NUMPAD1: currentColor = Color.RED; break;
          case NUMPAD2:  currentColor = Color.BLUE; break;
          case NUMPAD3: currentColor = Color.GREEN; break;
          default:
            break;
        }
      });
      pane.requestFocus();

      pane.setOnMouseClicked(e -> {
          double x = e.getX();
          double y = e.getY();
          int index = 0;
          int size = dotList.size();
          if (size !=0 && index == size) {
              Dot check = dotList.get(index);
              if (check.contains(x, y)) {
                  dotList.remove(index);
                  pane.getChildren().remove(index); //This is may be wrong
                  size = dotList.size();
              }
              index++;
          }
          Dot newDot = new Dot(x ,y);
          dotList.add(newDot);
          pane.getChildren().add(newDot); ///This adds a new dot, this works


      });
      pane.requestFocus();

    // Your code ends here

    stage.show(); // makes the window visible to the user
}