Unity3D Code Snippets of Interest from AngryBirdsClone

BrickCollision.cs

public float Health = 70f;

void OnCollisionEnter2D(Collision2D col)
{
    if (col.gameObject.GetComponent<Rigidbody2D>() == null) return;

    float damage = col.gameObject.GetComponent<Rigidbody2D>().velocity.magnitude * 10;
    //don't play audio for small damages
    if (damage >= 10)
        GetComponent<AudioSource>().Play();
    //decrease health according to magnitude of the object that hit us
    Health -= damage;
    //if health is 0, destroy the block
    if (Health <= 0) Destroy(this.gameObject);
}

CameraFixAspectRatio.cs

// This is attached to the Main Camera Object

void Start()
{
    Camera camera = GetComponent<Camera>();
    float aspect = Mathf.Round(camera.aspect * 100f) / 100f;

    //this is to be altered different Windows Phone 8 aspect ratios
    //there should be a better way of doing this
    if (aspect == 0.6f) //WXGA or WVGA
        camera.orthographicSize = 5;
    else if (aspect == 0.56f) //720p
    {
        camera.orthographicSize = 4.6f;
    }
}

CameraFollow.cs

[HideInInspector]
public Vector3 StartingPosition;

private const float minCameraX = 0;
private const float maxCameraX = 13;
[HideInInspector]
public bool IsFollowing;
[HideInInspector]
public Transform BirdToFollow;

// Use this for initialization
void Start()
{
    StartingPosition = transform.position;
}

// Update is called once per frame
void Update()
{
    if (IsFollowing)
    {
        if (BirdToFollow != null) //bird will be destroyed if it goes out of the scene
        {
            var birdPosition = BirdToFollow.transform.position;
            float x = Mathf.Clamp(birdPosition.x, minCameraX, maxCameraX);
            //camera follows bird's x position
            transform.position = new Vector3(x, StartingPosition.y, StartingPosition.z);
        }
        else
            IsFollowing = false;
    }
}

DestroyerBoundaries.cs

void OnTriggerEnter2D(Collider2D col)
{
    //destroyers are located in the borders of the screen
    //if something collides with them, the'll destroy it
    string tag = col.gameObject.tag;
    if(tag == "Bird" || tag == "Pig" || tag == "Brick")
    {
        Destroy(col.gameObject);
    }
}

GameManagerInit.cs

Camera camera;
Vector3 previousCameraTransform;
public float ParallaxFactor;

camera = Camera.main;
previousCameraTransform = camera.transform.position;

void Start()
{
    CurrentGameState = GameState.Start;
    slingshot.enabled = false;
    //find all relevant game objects
    Bricks = new List<GameObject>(GameObject.FindGameObjectsWithTag("Brick"));
    Birds = new List<GameObject>(GameObject.FindGameObjectsWithTag("Bird"));
    Pigs = new List<GameObject>(GameObject.FindGameObjectsWithTag("Pig"));
    //unsubscribe and resubscribe from the event
    //this ensures that we subscribe only once
    slingshot.BirdThrown -= Slingshot_BirdThrown; slingshot.BirdThrown += Slingshot_BirdThrown;
}

ParallaxScrolling.cs

Vector3 previousCameraTransform;

void Update () {
      Vector3 delta = camera.transform.position - previousCameraTransform;
      delta.y = 0; delta.z = 0;
      transform.position += delta / ParallaxFactor;
      
      previousCameraTransform = camera.transform.position;
}

PigCollision.cs

public float Health = 150f;
public Sprite SpriteShownWhenHurt;
private float ChangeSpriteHealth;

// Use this for initialization
void Start()
{
    ChangeSpriteHealth = Health - 30f;
}

// Collision with a Collider2D
void OnCollisionEnter2D(Collision2D col)
{
    if (col.gameObject.GetComponent<Rigidbody2D>() == null) return;

    //if we are hit by a bird
    if (col.gameObject.tag == "Bird")
    {
        GetComponent<AudioSource>().Play();
        Destroy(gameObject);
    }
    else //we're hit by something else
    {
        //calculate the damage via the hit object velocity
        float damage = col.gameObject.GetComponent<Rigidbody2D>().velocity.magnitude * 10;
        Health -= damage;
        //don't play sound for small damage
        if (damage >= 10)
            GetComponent<AudioSource>().Play();

        if (Health < ChangeSpriteHealth)
        {
            //change the shown sprite
            GetComponent<SpriteRenderer>().sprite = SpriteShownWhenHurt;
        }
        if (Health <= 0) Destroy(this.gameObject);
    }
}

SlingShotBirdThrow.cs

[HideInInspector]
//the bird to throw
public GameObject BirdToThrow;
//a vector that points in the middle between left and right parts of the slingshot
private Vector3 SlingshotMiddleVector;

private void ThrowBird(float distance)
{
    //get velocity
    Vector3 velocity = SlingshotMiddleVector - BirdToThrow.transform.position;
    BirdToThrow.GetComponent<Bird>().OnThrow(); //make the bird aware of it
    //old and alternative way
    //BirdToThrow.GetComponent<Rigidbody2D>().AddForce
    //    (new Vector2(v2.x, v2.y) * ThrowSpeed * distance * 300 * Time.deltaTime);
    //set the velocity
    BirdToThrow.GetComponent<Rigidbody2D>().velocity = new Vector2(velocity.x, velocity.y) * ThrowSpeed * distance;
    
    //notify interested parties that the bird was thrown
    if (BirdThrown != null)
        BirdThrown(this, EventArgs.Empty);
}

SlingShotInit.cs

//the left and right parts of the slingshot
public Transform LeftSlingshotOrigin, RightSlingshotOrigin;

//two line renderers to simulate the "strings" of the slingshot
public LineRenderer SlingshotLineRenderer1;
public LineRenderer SlingshotLineRenderer2;

// Use this for initialization
void Start()
{
    //set the sorting layer name for the line renderers
    //for the slingshot renderers this did not work so I
    //set the z on the background sprites to 10
    //hope there's a better way around that!
    SlingshotLineRenderer1.sortingLayerName = "Foreground";
    SlingshotLineRenderer2.sortingLayerName = "Foreground";
    TrajectoryLineRenderer.sortingLayerName = "Foreground";

    slingshotState = SlingshotState.Idle;
    SlingshotLineRenderer1.SetPosition(0, LeftSlingshotOrigin.position);
    SlingshotLineRenderer2.SetPosition(0, RightSlingshotOrigin.position);

    //pointing at the middle position of the two vectors
    SlingshotMiddleVector = new Vector3((LeftSlingshotOrigin.position.x + RightSlingshotOrigin.position.x) / 2,
        (LeftSlingshotOrigin.position.y + RightSlingshotOrigin.position.y) / 2, 0);
}

SlingShotLineRenderers.cs

[HideInInspector]
//the bird to throw
public GameObject BirdToThrow;
//this linerenderer will draw the projected trajectory of the thrown bird
public LineRenderer TrajectoryLineRenderer;

void DisplayTrajectoryLineRenderer2(float distance)
{
    SetTrajectoryLineRenderesActive(true);
    Vector3 v2 = SlingshotMiddleVector - BirdToThrow.transform.position;
    int segmentCount = 15;
    float segmentScale = 2;
    Vector2[] segments = new Vector2[segmentCount];

    // The first line point is wherever the player's cannon, etc is
    segments[0] = BirdToThrow.transform.position;

    // The initial velocity
    Vector2 segVelocity = new Vector2(v2.x, v2.y) * ThrowSpeed * distance;

    float angle = Vector2.Angle(segVelocity, new Vector2(1, 0));
    float time = segmentScale / segVelocity.magnitude;
    for (int i = 1; i < segmentCount; i++)
    {
        //x axis: spaceX = initialSpaceX + velocityX * time
        //y axis: spaceY = initialSpaceY + velocityY * time + 1/2 * accelerationY * time ^ 2
        //both (vector) space = initialSpace + velocity * time + 1/2 * acceleration * time ^ 2
        float time2 = i * Time.fixedDeltaTime * 5;
        segments[i] = segments[0] + segVelocity * time2 + 0.5f * Physics2D.gravity * Mathf.Pow(time2, 2);
    }

    TrajectoryLineRenderer.SetVertexCount(segmentCount);
    for (int i = 0; i < segmentCount; i++)
        TrajectoryLineRenderer.SetPosition(i, segments[i]);
}

SlingShotUpdate.cs

// Update is called once per frame
void Update()
{
    switch (slingshotState)
    {
        case SlingshotState.Idle:
            //fix bird's position
            InitializeBird();
            //display the slingshot "strings"
            DisplaySlingshotLineRenderers();
            if (Input.GetMouseButtonDown(0))
            {
                //get the point on screen user has tapped
                Vector3 location = Camera.main.ScreenToWorldPoint(Input.mousePosition);
                //if user has tapped onto the bird
                if (BirdToThrow.GetComponent<CircleCollider2D>() == Physics2D.OverlapPoint(location))
                {
                    slingshotState = SlingshotState.UserPulling;
                }
            }
            break;
        case SlingshotState.UserPulling:
            DisplaySlingshotLineRenderers();

            if (Input.GetMouseButton(0))
            {
                //get where user is tapping
                Vector3 location = Camera.main.ScreenToWorldPoint(Input.mousePosition);
                location.z = 0;
                //we will let the user pull the bird up to a maximum distance
                if (Vector3.Distance(location, SlingshotMiddleVector) > 1.5f)
                {
                    //basic vector maths :)
                    var maxPosition = (location - SlingshotMiddleVector).normalized * 1.5f + SlingshotMiddleVector;
                    BirdToThrow.transform.position = maxPosition;
                }
                else
                {
                    BirdToThrow.transform.position = location;
                }
                float distance = Vector3.Distance(SlingshotMiddleVector, BirdToThrow.transform.position);
                //display projected trajectory based on the distance
                DisplayTrajectoryLineRenderer2(distance);
            }
            else//user has removed the tap 
            {
                SetTrajectoryLineRenderesActive(false);
                //throw the bird!!!
                TimeSinceThrown = Time.time;
                float distance = Vector3.Distance(SlingshotMiddleVector, BirdToThrow.transform.position);
                if (distance > 1)
                {
                    SetSlingshotLineRenderersActive(false);
                    slingshotState = SlingshotState.BirdFlying;
                    ThrowBird(distance);
                }
                else//not pulled long enough, so reinitiate it
                {
                    //distance/10 was found with trial and error :)
                    //animate the bird to the wait position
                    BirdToThrow.transform.positionTo(distance / 10, //duration
                        BirdWaitPosition.transform.position). //final position
                        setOnCompleteHandler((x) =>
                    {
                        x.complete();
                        x.destroy();
                        InitializeBird();
                    });

                }
            }
            break;
        case SlingshotState.BirdFlying:
            break;
        default:
            break;
    }
}