How to collide obstacles each other like flappy crush game in unity?

i try to collide obstacle each other each other on y axis like flappy crush game so any how can do?this is reference link:Flappy Crush iOS / Android Gameplay Trailer HD - YouTube

------------- About collision ----------------

Check the documentation :

Your 2D birds and obstacle need to have a 2D collider on their sprite. Put on these elements a custom script that implements OnTriggerEnter2D . This method will be called when an other collider enter in their area.

You could for example put it on the obstacle and do something like this :

 // We are in the script of the obstacle
 void OnTriggerEnter2D(Collider2D other) 
`{
     // "other" is the bird that collides with it , you kill him
     Destroy(other.gameObject);
 }

------------- About moving obstacles ----------------

You have 1 pipe up and 1 pipe down. And at each frame, you make them move until they collide.

// Set this to 1 or -1 to make your pipe move up or down
public int direction;

// The speed of the pipe
public float speed;

void Update()
{
  // use the Translate method to move a transform
  transform.Translate(0f, speed*direction*Time.deltaTime, 0f);
}

// Then check the collision between the obstacles
  void OnTriggerEnter2D(Collider2D other) 
 `{
     // Let's assume that you identify your pipe with a tag
      if(other.tag == "Pipe")
      {
           // Inverse the direction so the pipes get back to their positions
            direction *= -1;
      }
  }

Complete this with something similar to inverse the position again when the pipes are back to their initial positions.
Notice that your 2 pipes always have an opposed direction at the same time.

I wrote this in blind but this is the idea.