code

public Rigidbody2D bird;
    public Transform slingshotPivot;

    private Vector2 startPos;
    private bool isDragging = false;

    void Start()
    {
        startPos = bird.position;
    }

    void Update()
    {
        if (Input.GetMouseButtonDown(0))
            isDragging = true;

        if (Input.GetMouseButtonUp(0) && isDragging)
        {
            isDragging = false;
            LaunchBird();
        }

        if (isDragging)
         DragBird();
    }

    void DragBird()
    {
        Vector3 mousePos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
        mousePos.z = 0;
        bird.position = mousePos;
    }

    void LaunchBird()
    {
        Vector2 launchVelocity = (startPos - bird.position) * 5;
        bird.isKinematic = false;
        bird.AddForce(launchVelocity, ForceMode2D.Impulse);
    }