Не растет змейка после поедания яблока. Все валидации пройдены.

package com.javarush.games.snake;

import com.javarush.engine.cell.*;


public class SnakeGame extends Game{

    public static void main(String[] args) {

    }
    public static final int WIDTH = 15;
    public static final int HEIGHT = 15;
    private Snake snake;
    private int turnDelay;
    private Apple apple;
    private boolean isGameStopped;
    private static final int GOAL = 28;
    private int score;

    public void initialize(){
        setScreenSize(WIDTH, HEIGHT);


        createGame();

    }

    private void createGame(){
        score = 0;
        setScore(score);
        snake = new Snake(WIDTH/2,HEIGHT/2);
        createNewApple();
        isGameStopped = false;
        drawScene();
        turnDelay = 300;
        setTurnTimer(turnDelay);
    }

    private void drawScene(){
        for (int x = 0; x < WIDTH; x++) {
            for (int y = 0; y < HEIGHT; y++) {
                setCellValueEx(x, y, Color.DARKSEAGREEN,"");
            }
        }
        snake.draw(this);
        apple.draw(this);
    }

    @Override
    public void onTurn(int step) {
        snake.move(apple);
        if (!apple.isAlive){
            score += 5;
            setScore(score);
            turnDelay -= 10;
            setTurnTimer(turnDelay);
            createNewApple();
        }
        if (!snake.isAlive){
            gameOver();
        }
        if (snake.getLength()> GOAL){
            win();
        }
        drawScene();
    }

    @Override
    public void onKeyPress(Key key) {
        if (key == Key.LEFT){
            snake.setDirection(Direction.LEFT);
        }
        else  if (key == Key.RIGHT){
            snake.setDirection(Direction.RIGHT);
        }
        else  if (key == Key.DOWN){
            snake.setDirection(Direction.DOWN);
        }
        else  if (key == Key.UP){
            snake.setDirection(Direction.UP);
        }
        else if (key == Key.SPACE && isGameStopped){
            createGame();
        }
    }
    private void createNewApple(){
        apple = new Apple(getRandomNumber(WIDTH), getRandomNumber(HEIGHT));
        while (snake.checkCollision(apple))
            apple = new Apple(getRandomNumber(WIDTH), getRandomNumber(HEIGHT));

    }

    private void gameOver(){
        stopTurnTimer();
        isGameStopped = true;
        showMessageDialog(Color.BLUE,"GAME OVER", Color.BLACK, 50);
    }

    private void win(){
        stopTurnTimer();
        isGameStopped = true;
        showMessageDialog(Color.RED, "WIN", Color.BLACK, 75);
    }
}

package com.javarush.games.snake;

import com.javarush.engine.cell.Game;
import com.javarush.engine.cell.*;

import java.util.ArrayList;
import java.util.List;

public class Snake {
    public boolean isAlive = true;
    private static final String HEAD_SIGN = "\uD83D\uDC7E";
    private static final String BODY_SIGN = "\u26AB";
    private Direction direction = Direction.LEFT;
    private List<GameObject> snakeParts = new ArrayList<GameObject>();
    public void draw (Game game){
        if (isAlive) {
            for (int i = 0; i < snakeParts.size(); i++) {
                if (i == 0) {
                    game.setCellValueEx(snakeParts.get(i).x, snakeParts.get(i).y, Color.NONE, HEAD_SIGN,Color.BLACK, 75);
                }
                else game.setCellValueEx(snakeParts.get(i).x, snakeParts.get(i).y, Color.NONE, BODY_SIGN,Color.BLACK, 75);
            }
        }
        else {
            for (int i = 0; i < snakeParts.size(); i++) {
                if (i == 0) {
                    game.setCellValueEx(snakeParts.get(i).x, snakeParts.get(i).y, Color.NONE, HEAD_SIGN,Color.RED, 75);
                }
                else game.setCellValueEx(snakeParts.get(i).x, snakeParts.get(i).y, Color.NONE, BODY_SIGN,Color.RED, 75);
            }
            }

        }



    public Snake(int x, int y) {
        for (int i = 0; i < 3; i++) snakeParts.add(new GameObject(x + i, y));
    }


    public void move(Apple apple){
        GameObject cords = createNewHead();


        if (apple.x == cords.x && apple.y == cords.y){
            apple.isAlive = false;
        }
        else {
            if (checkCollision(cords)){
                isAlive = false;
            }
            else {
                snakeParts.add(0, cords);
                removeTail();
            }
        }
    }
    public GameObject createNewHead(){
       if (direction == Direction.LEFT){
           return new GameObject(snakeParts.get(0).x-1, snakeParts.get(0).y);
       }
       else if(direction == Direction.RIGHT){
           return new GameObject(snakeParts.get(0).x+1, snakeParts.get(0).y);
       }
       else if (direction == Direction.DOWN){
           return new GameObject(snakeParts.get(0).x, snakeParts.get(0).y +1);
       }
       else return new GameObject(snakeParts.get(0).x, snakeParts.get(0).y-1);
    }
    public void removeTail(){
        snakeParts.remove(snakeParts.size()-1);
    }

    public void setDirection(Direction direction) {
        if (direction == Direction.LEFT && this.direction != Direction.RIGHT && snakeParts.get(0).y != snakeParts.get(1).y){
            this.direction = direction;

        }
        else  if (direction == Direction.DOWN && this.direction != Direction.UP && snakeParts.get(0).x != snakeParts.get(1).x){
 this.direction = direction;
        }
        else  if (direction == Direction.UP && this.direction != Direction.DOWN && snakeParts.get(0).x != snakeParts.get(1).x){
            this.direction = direction;
        }
        else  if (direction == Direction.RIGHT && this.direction != Direction.LEFT && snakeParts.get(0).y != snakeParts.get(1).y){
            this.direction = direction;
        }

    }
    public boolean checkCollision(GameObject gameObject){
        boolean result = false;
        for (int i = 0; i < snakeParts.size(); i++ ){
            if (snakeParts.get(i).x == gameObject.x && snakeParts.get(i).y == gameObject.y){
                isAlive = false;
                result = true;
            }

        }
        return result;
    }

    public int getLength(){
        return snakeParts.size();
    }


}

package com.javarush.games.snake;

import com.javarush.engine.cell.Color;
import com.javarush.engine.cell.Game;
import com.javarush.engine.cell.*;

public class Apple extends GameObject {
    public boolean isAlive = true;
    private static final String APPLE_SIGN = "\uD83C\uDF4E";
    public Apple(int x, int y) {
        super(x, y);
    }

    public void draw(Game game){
        game.setCellValueEx(x,y, Color.NONE,APPLE_SIGN,Color.GREEN, 75 );
    }
}

package com.javarush.games.snake;

public enum Direction {
    UP,
    RIGHT,
    DOWN,
    LEFT;

}

package com.javarush.games.snake;

public class GameObject {
    public int x;
    public  int y;

    public GameObject(int x, int y) {
        this.x = x;
        this.y = y;
    }
}