Scrolling Repeating Backgrounds

Checked with version: 5.5

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Difficulty: Beginner

In this beginner friendly live training we will look at creating a simple 2D Flappy Bird style game. We'll cover best practices for infinite or endless games, basic object pooling and creating cartoon physics effects.

Scrolling Repeating Backgrounds

Beginner 2D Game Creation

ScrollingObject

Code snippet

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

public class ScrollingObject : MonoBehaviour 
{
    private Rigidbody2D rb2d;

    // Use this for initialization
    void Start () 
    {
        //Get and store a reference to the Rigidbody2D attached to this GameObject.
        rb2d = GetComponent<Rigidbody2D>();

        //Start the object moving.
        rb2d.velocity = new Vector2 (GameControl.instance.scrollSpeed, 0);
    }

    void Update()
    {
        // If the game is over, stop scrolling.
        if(GameControl.instance.gameOver == true)
        {
            rb2d.velocity = Vector2.zero;
        }
    }
}

RepeatingBackground

Code snippet

using UnityEngine;
using System.Collections;

public class RepeatingBackground : MonoBehaviour 
{
    
    private BoxCollider2D groundCollider;       //This stores a reference to the collider attached to the Ground.
    private float groundHorizontalLength;       //A float to store the x-axis length of the collider2D attached to the Ground GameObject.

    //Awake is called before Start.
    private void Awake ()
    {
        //Get and store a reference to the collider2D attached to Ground.
        groundCollider = GetComponent<BoxCollider2D> ();
        //Store the size of the collider along the x axis (its length in units).
        groundHorizontalLength = groundCollider.size.x;
    }

    //Update runs once per frame
    private void Update()
    {
        //Check if the difference along the x axis between the main Camera and the position of the object this is attached to is greater than groundHorizontalLength.
        if (transform.position.x < -groundHorizontalLength)
        {
            //If true, this means this object is no longer visible and we can safely move it forward to be re-used.
            RepositionBackground ();
        }
    }

    //Moves the object this script is attached to right in order to create our looping background effect.
    private void RepositionBackground()
    {
        //This is how far to the right we will move our background object, in this case, twice its length. This will position it directly to the right of the currently visible background object.
        Vector2 groundOffSet = new Vector2(groundHorizontalLength * 2f, 0);

        //Move this object from it's position offscreen, behind the player, to the new position off-camera in front of the player.
        transform.position = (Vector2) transform.position + groundOffSet;
    }
}