Unity3d + tk2d sprite movement

Unity3d object (sprite) movement

using UnityEngine;

public class MoveSprite : MonoBehaviour
{
  public tk2dSprite sprite;   
  float Speed = 50f; // 50 meters per second
  
  Vector3 TopRightPoint;
  Vector3 BottomLeftPoint;
  
  void Start()
  {
    BottomLeftPoint = Camera.main.ScreenToWorldPoint( Vector3.zero );
    TopRightPoint   = Camera.main.ScreenToWorldPoint( new Vector3( Screen.width, Screen.height ));
  }
  
  void Update()
  {
    sprite.transform.position += new Vector3( Speed * direction.x * Time.deltaTime, 0.0f, 0.0f ); 		

    if ( sprite.transform.position.x >= TopRightPoint.x )
    {
      direction = Vector3.left;	
    }

    if ( sprite.transform.position.x <= BottomLeftPoint.x )
    {
      direction = Vector3.right;	
    }
  }
}