Creating endless room for endless falling game

I'm using this tutorial to practice creating an endless runner game : http://www.raywenderlich.com/69544/make-game-like-jetpack-joyride-unity-2d-part-2

But now I want to make a vertical endless which has the character falling down.

I have this code but the rooms weren't spawning correctly.

 using UnityEngine; using System.Collections; using System.Collections.Generic;
 
 public class GenerateLevel : MonoBehaviour {          Prefabs     public GameObject[] availableRooms;
               public List<GameObject> currentRooms;          private float screenWidthInPoints;          void Start () {         float height = 2f * Camera.main.orthographicSize;
                  screenWidthInPoints = height * Camera.main.aspect;     }          void AddRoom(float farhtestRoomEndY)     {
 
         int randomRoomIndex = Random.Range(0, availableRooms.Length);
                  GameObject room = (GameObject)Instantiate(availableRooms[randomRoomIndex]);
                  float roomHeight = room.transform.FindChild("floor").localScale.y;
                  float roomCenter = farhtestRoomEndY + roomHeight * 0.5f;
 
         room.transform.position = new Vector3(0, roomCenter, 0);
                  currentRooms.Add(room);     }          void GenerateRoomIfRequired()     {         List<GameObject> roomsToRemove = new List<GameObject>();
                  bool addRooms = true;        
                  float playerY = transform.position.y;
                  float removeRoomY = playerY - screenWidthInPoints;        
                  float addRoomY = playerY + screenWidthInPoints;
                  float farthestRoomEndY = 0;
                  foreach(var room in currentRooms)         {             float roomHeight = room.transform.FindChild("floor").localScale.y;             float roomStartY = room.transform.position.y - (roomHeight * 0.5f);                 float roomEndY = roomStartY - roomHeight;
                          if (roomStartY > addRoomY)
                 addRooms = false;
 
             if (roomEndY < removeRoomY)
                 roomsToRemove.Add(room);
                          farthestRoomEndY = Mathf.Min(farthestRoomEndY, roomEndY);         }
                  foreach(var room in roomsToRemove)         {             currentRooms.Remove(room);             Destroy(room);                     }
                  if (addRooms)             AddRoom(farthestRoomEndY);     }          void Update () {
              }          void FixedUpdate ()      {             GenerateRoomIfRequired();     } }

 

What's wrong with the code?