Play Again

Lesson 12 of 14 in Coddy's Unity Game: Snake 3D course.

When the snake dies, a Game Over panel comes up with a Play Again button. The panel is in the HUD and starts hidden, and SetActive(true) shows it. The snake knows when it dies, and the GameManager owns the screens, so Die() calls a public GameOver() on the GameManager.

Play Again starts over by loading the scene again. Every object comes back as the scene has it: the snake on its first cell with two segments, the score at 0, the panel hidden. A racing game's Retry button is wired the same way:

void Start()
{
    retryButton.onClick.AddListener(Retry);
}

void Retry()
{
    SceneManager.LoadScene("Track1");
}

Loading by name ties the button to one scene. SceneManager.GetActiveScene().buildIndex is the scene that is running, so loading it restarts whichever scene the button is in. The new scene has a new GameManager, whose Awake() sets Instance again, so the new snake talks to the new GameManager.

Challenge

Medium

The HUD has a hidden GameOverPanel with a PlayAgainButton, and the scene sets both on GameManager.

In GameManager, add using UnityEngine.UI;, using UnityEngine.SceneManagement;, public GameObject gameOverPanel; and public Button playAgainButton;.
Write public void GameOver(), which shows the panel.
Write void PlayAgain(), which loads the active scene again, and in Start() make the button call it.
In Snake's Die(), call GameOver().

Press Play, crash, play again, then press Check.

Try it yourself

using System.Collections.Generic;
using UnityEngine;
using TMPro;

public class GameManager : MonoBehaviour
{
    public static GameManager Instance;

    public Snake snake;
    public GameObject foodPrefab;
    public TMP_Text scoreText;
    private Transform food;
    private int score;

    void Awake()
    {
        Instance = this;
    }

    void Start()
    {
        scoreText.text = "Score: 0";
        food = Instantiate(foodPrefab).transform;
        MoveFood();
    }

    public bool IsFood(Vector3 cell)
    {
        return cell == food.position;
    }

    public void Eat()
    {
        score++;
        scoreText.text = "Score: " + score;
        MoveFood();
    }

    void MoveFood()
    {
        List<Vector3> free = new List<Vector3>();
        for (int x = -snake.edge; x <= snake.edge; x++)
        {
            for (int z = -snake.edge; z <= snake.edge; z++)
            {
                Vector3 cell = new Vector3(x, 0f, z);
                if (!snake.Occupies(cell))
                {
                    free.Add(cell);
                }
            }
        }
        food.position = free[Random.Range(0, free.Count)];
    }
}