How does this conditional evaluate? -- Repeating Background Script

Questions & Answers
1

Hi. I am following along with Unity’s “Flappy Bird Tutorial”, but I do not understand a line of the code in the repeating background script.

// Use this for initialization
	void Start () 
	{
		groundCollider = GetComponent<BoxCollider2D> (); 
		groundHorizontalLength = groundCollider.size.x;
	}
	
	// Update is called once per frame
	void Update () 
	{
		if (transform.position.x < -groundHorizontalLength) 
		{
			RepositionBackground (); 
		}
	}

	// Repositions background
	private void RepositionBackground()
	{
		Vector2 groundOffset = new Vector2 (groundHorizontalLength * 2f, 0); 
		transform.position = (Vector2)transform.position + groundOffset;
	}

Mainly, I don’t understand the conditional. Could someone explain it in simple terms? Thank you in advance.

2

From what I understand, this script repositions the background if your character falls behind the ground collider. groundHorizontalLength is the size of the collider that kills the player. If the player moves out of it in a way that if he fell down he wouldn’t hit it and end the game, the background moves you twice the size of the collider forward. I don’t know why it’s groundHorizontalLength * 2f instead of groundHorizontalLength in the groundOffset, but maybe you understand.