Move a ball horizontally left and right but restricting forwards and backwards motion unity 2d

Question

I am trying to develop an endless runner where there is a sphere as the player and it is moving left and right following the position of a finger on a touch screen. However, when I try to do this I cannot get the player to lock on the Y-axis. I want a constant force that speeds up overtime which I have using the constant force 2d supplied by unity. I have two versions of code, the first follows the finger but the player is able to move up and down as well:

using UnityEngine;
using System.Collections;

public class Test : MonoBehaviour
{
    public GameObject character;
    public float speed = 500.0f;

    void Start()
    {
        Input.multiTouchEnabled = false;
    }

    void Update()
    {
        if (Input.touchCount == 1 && Input.GetTouch(0).phase == TouchPhase.Moved)
        {
            Vector2 target = Camera.main.ScreenToWorldPoint(
                              new Vector2(Input.mousePosition.x, Input.mousePosition.y));
            character.transform.Translate(Vector3.MoveTowards(character.transform.position, 
                              target, speed * Time.deltaTime) - character.transform.position);
    }
}

The second code I have allows the player to move left and right by tapping rather than following but is still sloppy:

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

public class PlayerMovement : MonoBehaviour
{
    public Rigidbody2D rb;

    public float sidewaysForce = 500f;
    // Start is called before the first frame update
    void Start()
    {
        rb = GetComponent<Rigidbody2D>();
    }

    // Update is called once per frame
    void Update()
    {
        {
            foreach (Touch touch in Input.touches)
            {
                if (touch.position.x < Screen.width / 2)
                {
                    rb.velocity = new Vector2(sidewaysForce * -1, rb.velocity.y);
                }
                if (touch.position.x > Screen.width / 2)
                {
                    rb.velocity = new Vector2(sidewaysForce * +1, rb.velocity.y);
                }
            }
        }
    }
}

Any help on this would be awesome Thanks!!!

Answer 1

in 2d horizon is X axis. for restriction you can simple put a restricting object or read borders of your camera.assume you have a minX and minY empty objects. so you will have:

    [SerializeField] private Transform minX;
    [SerializeField] private Transform maxX;
void Update()
{
  if (transform.position.x < minX.position.x) { transform.position = new Vector3(minX.position.x,transform.position.y,transform.position.z); }
  if (transform.position.x > maxX.position.x) { transform.position = new Vector3(maxX.position.x, transform.position.y, transform.position.z); }
}