How to make goalKeeper move within post but not move towards to the player?

Question

Hello so basically I make a 2d top-down soccer game but I have to trouble with GK AI, I want to GK is followed the ball but not move toward on it

let say (Enemy = GK)

so when the player moves to the left or right the enemy will follow to the right or left not The Yaxis but in X-axis with guarding the post or Y=0

my default enemy movement is like this :

if (gameObject.CompareTag("GK"))
        {

            anim.SetBool("GKRun", false);
            gkballInRange = Physics2D.OverlapCircle(transform.position, gkballRange, playerMask);
            float distancePlayer = Vector2.Distance(target.position, transform.position);

            if (gkballInRange)
            {
                if (distancePlayer <= gkballRange)
                {
                    //Animation
                    anim.SetBool("GKRun", true);
                    transform.Translate(0, -speed * Time.deltaTime, 0);
                }
            }

        }

in that scrip, when the ball is on the range the GK is moving to the ball just that. maybe anyone can explain to me how to do it?

Answer 1

OK, this is the situation you have:

You can obtain the GK-to-Player vector by doing target.Position - transform.Position, and you can use that vector both to determine how the goalkeeper should move and to check if the player is within the goalkeeper's range. I'll refer to this vector as relativePlayerPosition.

Currently, though, you're just calculating the distance to the player, and loosing any information about directions:

float distancePlayer = Vector2.Distance(target.position, transform.position);

If you look at the docs for Vector2.Distance, you'll see that it's calculated as
(target.position - transform.position).magnitude.

So, you can do the same thing "manually", but keep the intermediate result. Calculate the relative position vector and store it into a variable, then use magnitude to get the distance:

Vector2 relativePlayerPosition = target.position - transform.position;
float distancePlayer = relativePlayerPosition.magnitude;

If the player is to the left of the goalie, the x component of this vector will be negative. If the player is to the right, it will be positive. You can use this fact to change the direction towards which the goalkeeper moves.

To obtain the sign of the x component, use the Mathf.Sign function (returns -1 for negative values, and 1 otherwise).

float xDirection = Mathf.Sign(relativePlayerPosition.x);

Finally, use this to modify the direction (sign) of the x parameter for the Translate method:

transform.Translate(xDirection * speed * Time.deltaTime, 0, 0);