how to move character move on a circular surface in only one direction?

Question

Making a 2d game:

I want to move character on circular surface only in one direction?

Script attached to child object is:

    public GameObject ball;
    float speed=2f;

    // Start is called before the first frame update
    void Start()
    {
        GetComponent<Rigidbody2D>();
    }

    // Update is called once per frame
    void Update()
    {
        Left();
    }

    void Left()
    {
        if(Input.GetKey(KeyCode.LeftArrow))
        {
            ball.GetComponent<Rigidbody2D>().AddForce(Vector3.forward * speed);
            //transform.Rotate(Vector2.left);
        }
    }

Note: character will move on a circular surface in only one direction...

Image reference:

Answer 1

you need polar coordiates. you need to find the position in polar coordintaes(radius,teta) to unity basic cartesian coordinates(x,y) you can move the object by changing the theta angle this is my example code:

private void FixedUpdate()
    {
        foreach (var item in PolarElements)
        {

            float x = item.radius * Mathf.Cos(item.myAngle);
            float y = item.radius * Mathf.Sin(item.myAngle);

            item.position = new Vector3(transform.position.x+  x,transform.position.y+y,transform.position.z);
            item.myAngle += item.speed;
        }
    }