Endless Runner: When I swipe up to jump, the player jumps but then moves left or right on the single up swipe

Question

I am making an endless runner mobile game. The PC controls work perfectly and the Touch/Swipe controls for Left and Right work too. The problem is when I swipe up to jump, the player jumps but then also either moves left or right (seemingly at random). For the life of me I cannot figure it out. This is my first C# project so my code/game is Frankenstein of tutorials and google searches. I found out about the rigidbody component a little too late but I don't want to start using it now if I don't have to... Please help, I am at a total loss. I would also like to apologise in advance if my code is extremely messy and incoherent, I have tried my best. Here is my Player movement script:

PC Controls

public class PlayerMove : MonoBehaviour
{
    public float moveSpeed = 8;
    public float leftRightSpeed = 7;
    static public bool canMove = false; 
    public KeyCode moveL;
    public KeyCode moveR;
    public float horizVel = 0;
    public int laneNum = 2;
    public string controlLocked = "n";
    private float speedUpTime;
    private float waitTime = 0.45f;
    private Vector3 startTouchPosition;
    private Vector3 endTouchPosition;
    public GroundCheck groundCheck;
    public float jumpForce=7;
    public float gravity = -9.81f;
    public float gravityScale = 3;
    public float jumpCoolDown = 0.5f;
    private float lastJumpTime = 0;
    float velocity;

    // Start is called before the first frame update
    void Start()
    {
        speedUpTime = Time.time;
    }

    // Update is called once per frame
    void Update()
    {
        if (Time.time - speedUpTime >= 10f)
        {
            moveSpeed += 1;
            leftRightSpeed +=1;
            waitTime -= 0.05f;
            speedUpTime = Time.time;
        }

        transform.position += new Vector3(horizVel, 0, moveSpeed) * Time.deltaTime;

        if((Input.GetKeyDown(moveL)) && (laneNum>1)&& (controlLocked == "n"))
        {
            horizVel = -leftRightSpeed;
            StartCoroutine(stopSlide());
            laneNum -= 1;
            controlLocked = "y";
        }

        if((Input.GetKeyDown(moveR)) && (laneNum<3)&& (controlLocked == "n"))
        {
            horizVel = leftRightSpeed;
            StartCoroutine(stopSlide());
            laneNum += 1;
            controlLocked = "y";
        }
        
        velocity += gravity * gravityScale * Time.deltaTime;
        if (groundCheck.isGrounded && velocity < 0)
        {
            velocity = 0;
            lastJumpTime = 0;
        }
        if (Input.GetKeyDown(KeyCode.Space) && (Time.time - lastJumpTime) > jumpCoolDown)
        {
            lastJumpTime = Time.time;
            velocity = jumpForce;
        }
        transform.Translate(new Vector3(0, velocity, 0) * Time.deltaTime);

Touch Controls

if (Input.touchCount > 0 && Input.GetTouch(0).phase == TouchPhase.Began)
        {
            startTouchPosition = Input.GetTouch(0).position;
        }
        
        if (Input.touchCount > 0 && Input.GetTouch(0).phase == TouchPhase.Ended)
        {
            endTouchPosition = Input.GetTouch(0).position;
            // Check for horizontal swipe
            if((endTouchPosition.x < startTouchPosition.x) && (laneNum>1)&& (controlLocked == "n"))
            {
                horizVel = -leftRightSpeed;
                StartCoroutine(stopSlide());
                laneNum -= 1;
                controlLocked = "y";
            }

            if((endTouchPosition.x > startTouchPosition.x) && (laneNum < 3) && (controlLocked == "n"))
            {
                horizVel = leftRightSpeed;
                StartCoroutine(stopSlide());
                laneNum += 1;
                controlLocked = "y";
            }
        
            // Check for vertical swipe
            if ((endTouchPosition.y > startTouchPosition.y) && (Time.time - lastJumpTime) > jumpCoolDown)
            {
                lastJumpTime = Time.time;
                velocity = jumpForce;
            }
        }
    }

     IEnumerator stopSlide()
    {
        yield return new WaitForSeconds(waitTime);
        horizVel = 0;
        controlLocked = "n";
    }
}

I've been at it for so many hours, I don't even remember what I've tried. Either the player stops moving, Right becomes Left, Jump is Right, Left is jump, etc...

Answer 1

Since you said the touch-controls were the issue, this answer will be focused on your second block of code.

The reason seems to be because when a player swipes up, their finger will almost never be at the same x-position. To illustrate this, try swiping up on your screen in an exact perfect line.

Computers take things very literally. So even being off by 0.0000001 is significant enough to be counted as less/more.

So what does this mean? When you swipe up, your fingers x and y position will change - causing both if-statements to activate

A fix that wouldn’t be too time-draining would be to create a dead-zone for swipes.

To put it simply, a dead-zone is a threshold that must be passed in addition to the action.

Here is an example of a dead-zone:

if(endPosition < startPosition - 2) { <SNIPPED> }
#                                ^ THIS IS THE DEADZONE