2D Game Proper Way To Keep Player On Screen

Hello everyone. I am using Unity 5.4.1 while I do the developer challenges from the Super Space Shooter tutorial. In the videos they started off with a 3D project, I started off as 2D, which created some challenges but it helped me learn. One of the developer challenges is to prevent the player from moving off screen. Doing some searches I found many suggestions and settled on one that seemed the most straight forward.

I would like to make sure this is correct and see if I can get some feedback on some odd behavior when I play it. First the code. Of course this is a bit more code that is needed to see how movement is done, but I like to make sure you have the full picture.

In the Ship.cs Start method I set the movement min/max range.

The Player.cs moves in the Update method but I try to prevent off screen movement in the LateUpdate method.

The Ship.cs

Code (CSharp):

1. using UnityEngine;
2.  
3. public class Ship : MonoBehaviour
4. {
5.  
6.     public int hitPoints = 30;
7.     public float fireDelay;
8.     public float speed;
9.     public bool enemyShip = false;
10.  
11.     public GameObject laserPrefab;
12.     public GameObject shieldPrefab;
13.     public float laserDistanceForward;
14.     public float laserDistanceRight;
15.     public Vector3 laserRotation;
16.    
17.     protected Vector3 movementRangeMin;
18.     protected Vector3 movementRangeMax;
19.  
20.     // Start is called just before any of the Update methods is called the first time
21.     public void Start()
22.     {
23.         //Find out the boundaries of the viewalbe screen
24.         SpriteRenderer renderer = gameObject.GetComponentInChildren<SpriteRenderer>();
25.         Vector3 bottomLeftWorldCoordinates = Camera.main.ViewportToWorldPoint(Vector3.zero);
26.         Vector3 topRightWorldCoordinates = Camera.main.ViewportToWorldPoint(new Vector3(1, 1, 0));
27.  
28.         movementRangeMin = bottomLeftWorldCoordinates + renderer.bounds.extents;
29.         movementRangeMax = topRightWorldCoordinates - renderer.bounds.extents;
30.     }
31.  
32.     protected bool canShoot = true;
33.  
34.     protected void ShootLaser()
35.     {
36.         if (enemyShip)
37.         {
38.             GameObject.Instantiate(laserPrefab, transform.position + Vector3.down * laserDistanceForward + Vector3.right * laserDistanceRight, Quaternion.Euler(laserRotation));
39.         }
40.         else
41.         {
42.             GameObject.Instantiate(laserPrefab, transform.position + Vector3.up * laserDistanceForward + Vector3.right * laserDistanceRight, Quaternion.Euler(laserRotation));
43.         }
44.         Invoke("EnableShoot", fireDelay);
45.     }
46.  
47.     protected void EnableShoot()
48.     {
49.         canShoot = true;
50.     }
51.  
52.     public virtual void CalculateHit(int amount)
53.     {
54.         hitPoints -= amount;
55.     }
56. }
57.  

The Player.cs

Code (CSharp):

1. using UnityEngine;
2.  
3. public class Player : Ship
4. {
5.     public EnvironmentManager environmentManager;
6.     public GameManager gameManager;
7.     public float backgroundMultiplier = 0.008f;
8.     [Range(0, 3)]
9.     private int playerLives;
10.  
11.     void Update()
12.     {
13.         if (Input.GetAxis("Horizontal") < 0)
14.         {
15.             // Left
16.             transform.position = Vector2.Lerp(transform.position, transform.position + Vector3.left, speed * Time.deltaTime);
17.             environmentManager.SetMovingHorizontalMultiplier(backgroundMultiplier);
18.         }
19.         else if (Input.GetAxis("Horizontal") > 0)
20.         {
21.             // Right
22.             transform.position = Vector2.Lerp(transform.position, transform.position + Vector3.right, speed * Time.deltaTime);
23.             environmentManager.SetMovingHorizontalMultiplier(-backgroundMultiplier);
24.         }
25.         else
26.         {
27.             environmentManager.SetMovingHorizontalMultiplier(0);
28.         }
29.  
30.         if (Input.GetAxis("Vertical") > 0)
31.         {
32.             // Forward
33.             transform.position = Vector2.Lerp(transform.position, transform.position + Vector3.up, speed * Time.deltaTime);
34.             environmentManager.SetMovingVerticallyMultiplier(-backgroundMultiplier);
35.         }
36.         else if (Input.GetAxis("Vertical") < 0)
37.         {
38.             // Backwards
39.             transform.position = Vector2.Lerp(transform.position, transform.position + Vector3.down, speed * Time.deltaTime);
40.             environmentManager.SetMovingVerticallyMultiplier(backgroundMultiplier);
41.         }
42.         else
43.         {
44.             environmentManager.SetMovingVerticallyMultiplier(0);
45.         }
46.  
47.         if (Input.GetAxis("Fire") > 0 && canShoot)
48.         {
49.             canShoot = false;
50.             ShootLaser();
51.         }
52.     }
53.  
54.     // LateUpdate is called every frame, if the Behaviour is enabled
55.     public void LateUpdate()
56.     {
57.         //Keep the player from going off screen
58.         Vector3 newPosition = transform.position;
59.         newPosition.x = Mathf.Clamp(newPosition.x, movementRangeMin.x, movementRangeMax.x);
60.         newPosition.y = Mathf.Clamp(newPosition.y, movementRangeMin.y, movementRangeMax.y);
61.         transform.Translate(newPosition - transform.position);
62.     }
63.  
64.     public override void CalculateHit(int amount)
65.     {
66.         int startHP = hitPoints;
67.         base.CalculateHit(amount);
68.         if (hitPoints < startHP)
69.         {
70.             gameManager.oUI.DecreasePlayerHealth();
71.         }
72.         if (hitPoints <= 0)
73.         {
74.             playerLives--;
75.             gameManager.oUI.DecreasePlayerLife();
76.             if (playerLives < 0)
77.             {
78.                 gameManager.EndGame();
79.             }
80.             else
81.             {
82.                 gameManager.oUI.ResetPlayerHealth();
83.                 hitPoints = 30;
84.             }
85.         }
86.     }
87.  
88.     public void SetPlayerLives(int amount)
89.     {
90.         playerLives = amount;
91.     }
92. }
93.  

The odd behavior happens when you keep trying to move to the left or down or both and you try to fire. It seems like the laser is being fired just before the LateUpdate fixes the player's position, so the laser hits the player's collider. If I increase the spawn distance of the laser from the player, it then appears the laser is not coming from the gun on the ship as its position left/right is wrong. Is there a good way to handle that behavior?

 

You can use Physics2D.IgnoreCollision to make the laser not collide with the owning ship.

https://docs.unity3d.com/ScriptReference/Physics2D.IgnoreCollision.html

Also, your LateUpdate clamping of position seems like a fine solution for a static game area.

 

Thank you very much! Both for the IgnoreCollision tip and the compliment on my clamping.