Huge C# Procedural Generation Errors. Why?

Hello, I've been using a tutorial I found to create a voxel system for the roguelike I'm making. I just really don't know where I went wrong since I wrote the identical code. Should the script have been cut into multiple scripts or what?

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 public class PolygonGenerator : MonoBehaviour {
     //This first list contains every vertex of the mesh that we are going to render.
     public List<Vector3> newVertices = new List<Vector3>();
 
     //The triangles tell Unity how to build each section of the mesh joining the vertices.
     public List<int> newTriangles = new List<int>();
 
     //The UV list is unimportant right now but it tells Unity how the texture is aligned
     //on each polygon.
     public List<Vector2> newUV = new List<Vector2>();
 
     public List<Vector3> colVertices = new List<Vector3> ();
     public List<int> colTriangles = new List<int>();
     private int colCount;
 
     private MeshCollider col;
 
 
     //A mesh is made up of the vertices, triangles and UVs we are going to define,
     //after we make them up we'll save them as this mesh.
     private Mesh mesh;
 
     private float tUnit = 0.25f;
     private Vector2 tStone = new Vector2 (0, 0);
     private Vector2 tGrass = new Vector2 (0, 1);
 
     private int squareCount;
     
     // Use this for initialization
     void Start () {
 
         mesh = GetComponent<MeshFilter> ().mesh;
 
         float x = transform.position.x;
         float y = transform.position.y;
         float z = transform.position.z;
 
         GenTerrain ();
         BuildMesh ();
         UpdateMesh ();
 
         col = GetComponent<MeshCollider> ();
 
 
     }
 
     void GenSquare(int x, int y, Vector2 texture){
 
         newVertices.Add(new Vector3 (x, y, z));
         newVertices.Add(new Vector3 (x + 1, y, z));
         newVertices.Add (new Vector3 (x + 1, y - 1, z));
         newVertices.Add (new Vector3 (x, y - 1, z));
         
         newTriangles.Add (squareCount*4);
         newTriangles.Add ((squareCount*4)+1);
         newTriangles.Add ((squareCount*4)+3);
         newTriangles.Add ((squareCount*4)+1);
         newTriangles.Add ((squareCount*4)+2);
         newTriangles.Add ((squareCount*4)+3);
         
         newUV.Add (new Vector2 (tUnit * texture.x, tUnit * texture.y + tUnit));
         newUV.Add (new Vector2 (tUnit * texture.x + tUnit, tUnit * texture.y + tUnit));
         newUV.Add (new Vector2 (tUnit * texture.x + tUnit, tUnit * texture.y));
         newUV.Add (new Vector2 (tUnit * texture.x, tUnit * texture.y));
 
         squareCount++;
         }
 
     // Update is called once per frame
     void Update () {
     
         mesh.Clear ();
         mesh.vertices = newVertices.ToArray ();
         mesh.triangles = newTriangles.ToArray ();
         mesh.uv = newUV.ToArray (); //Post-Initial Script Addition
         mesh.Optimize ();
         mesh.RecalculateNormals ();
 
     }
     void UpdateMesh () {
 
         mesh.Clear ();
         mesh.vertices = newVertices.ToArray ();
         mesh.triangles = newTriangles.ToArray ();
         mesh.uv = newUV.ToArray (); //Post-Initial Script Addition
         mesh.Optimize ();
         mesh.RecalculateNormals ();
 
         squareCount = 0;
         newVertices.Clear ();
         newTriangles.Clear ();
         newUV.Clear ();
 
         Mesh newMesh = new Mesh ();
         newMesh.vertices = colVertices.ToArray ();
         newMesh.triangles = colTriangles.ToArray ();
         col.sharedMesh = newMesh;
 
         colVertices.Clear ();
         colTriangles.Clear ();
         colCount = 0;
 
         }
 
     void GenCollider(int x, int y,){
         //Top
         colVertices.Add (new Vector3 (x , y , 1));
         colVertices.Add (new Vector3 (x + 1 , y , 1));
         colVertices.Add (new Vector3 (x + 1 , y , 0));
         colVertices.Add (new Vector3 (x , y , 0));
 
         ColliderTriangles ();
 
         colCount++;
 
         //Bot
         colVertices.Add (new Vector3 (x , y -1 , 0));
         colVertices.Add (new Vector3 (x + 1 , y -1 , 0));
         colVertices.Add (new Vector3 (x + 1 , y -1 , 1 ));
         colVertices.Add (new Vector3 (x , y -1 , 1 ));
 
         ColliderTriangles ();
 
         colCount++;
 
         //Left
         colVertices.Add (new Vector3 (x , y -1 , 1));
         colVertices.Add (new Vector3 (x , y , 1));
         colVertices.Add (new Vector3 (x , y , 0 ));
         colVertices.Add (new Vector3 (x , y -1 , 0));
 
         ColliderTriangles();
 
         colCount++;
 
         //Right
         colVertices.Add (new Vector3 (x +1 , y , 1));
         colVertices.Add (new Vector3 (x +1 , y -1 , 1));
         colVertices.Add (new Vector3 (x +1 , y -1 , 0));
         colVertices.Add (new Vector3 (x +1 , y , 0));
 
         ColliderTriangles ();
 
         colCount++;
     }
 
 
         void ColliderTriangles(){
         colTriangles.Add (colCount*4);
         colTriangles.Add ((colCount*4)+1);
         colTriangles.Add ((colCount*4)+3);
         colTriangles.Add ((colCount*4)+1);
         colTriangles.Add ((colCount*4)+2);
         colTriangles.Add ((colCount*4)+3);
 
         colCount++;
     }
 
     public byte[,] blocks;
 
     
     void GenTerrain(){
         blocks=new byte[10,10];
         
         for(int px=0; px<blocks.GetLength(0); px++) {
             for(int py=0;py<blocks.GetLength(1);py++){
                 if(py==5){
                     blocks[px,py]=2;
                 } else if(py<5){
                     blocks[px,py]=1;
                 }
             }
         }
     }
 
     void BuildMesh(){
         for (int px=0; px<blocks.GetLength(0); px++) {
             for(int py=0;py<blocks.GetLength (1);py++){
 
                 //If the block is not air.
                 if(blocks[px,py]);
 
                 //GenCollider here, this will apply it.
                 //To every block other than air.
                 GenCollider (px,py);
 
                 if(blocks[px,py]==1){
                     GenSquare (px,py,tStone);
                         else if(blocks[px,py]==2{
                     GenSquare(px,py,tGrass);
                     }
     }//End air block check.
    }
   }
  }
 }