Move ball at constant speed on screen

Ah, a Breakout game, I created one too. There are many way to deal with movement e.g. rigidbody.AddForce, or rigidbody.velocity = …; and change you make to rigidbody are physics based to the engine will check if movement is possible before actually doing it. Here is a link to Unity’s breakout game tutorial, and I’m sure a Google search will give you many.

Below is a Ball class I used. I think my game was top-down, so you should change the axis accordingly.

 public class Ball : MonoBehaviour
 {
     public float MinimumSpeed = 25;
     public float MaximumSpeed = 30;
 
     //To prevent the ball from keep bouncing horizontally we enforce a minimum vertical movement
     public float MinimumVerticalMovement = 0.1F;
 
     //Don't move the ball unless you tell it to
     private bool hasBeenLaunched = false;
 
     void Update()
     {
         if (hasBeenLaunched)
         {
             //Get current speed and direction
             Vector3 direction = rigidbody.velocity;
             float speed = direction.magnitude;
             direction.Normalize();
 
             //Make sure the ball never goes straight horizotal else it could never come down to the paddle.
             if (direction.z > -MinimumVerticalMovement && direction.z < MinimumVerticalMovement)
             {
                 //Adjust the y, make sure it keeps going into the direction it was going (up or down)
                 direction.z = direction.z < 0 ? -MinimumVerticalMovement : MinimumVerticalMovement;
 
                 //Adjust the x also as x + y = 1
                 direction.x = direction.x < 0 ? -1 + MinimumVerticalMovement : 1 - MinimumVerticalMovement;
                 
                 //Apply it back to the ball
                 rigidbody.velocity = direction * speed;   
             }
 
             if (speed < MinimumSpeed || speed > MaximumSpeed)
             {
                 //Limit the speed so it always above min en below max
                 speed = Mathf.Clamp(speed, MinimumSpeed, MaximumSpeed);
 
                 //Apply the limit
                 //Note that we don't use * Time.deltaTime here since we set the velocity once, not every frame.
                 rigidbody.velocity = direction * speed;   
             }
         }
     }
 
     //When the bottom of the field it hit destroy the ball. 
     private void OnTriggerEnter(Collider other)
     {
         if (other.name == "Bottom")
         {
             Destroy(this.gameObject);
         }
     }
 
     public void Launch()
     {
         //Create a random vector but make sure it always point "up" (z axis in this case) else it could be launched straight down
         Vector3 randomDirection = new Vector3(Random.Range(-1.0F, 1.0F), 0, Mathf.Abs(Random.value));
 
         //Make sure we start at the minimum speed limit
         randomDirection = randomDirection.normalized * MinimumSpeed;
 
         //Apply it to the rigidbody so it keeps moving into that direction, untill it hits a block or wall
         rigidbody.velocity = randomDirection;
 
         hasBeenLaunched = true;
     }
 }

Your code helped me alot. Thank you !!

@lordlycastle After an hour of searching, your code got me to the answer i was looking for, thanks!