u3d-cube-world/Assets/WorldController.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class WorldController : MonoBehaviour
{
    public GameObject block;
    public int worldSize = 2;
    public int worldHeight = 2; // y
    public int worldWidth = 2;  // x
    public int worldDepth = 2;  // z

    public IEnumerator BuildWorld()
    {
        for(int z = 0; z < worldDepth; z++) 
            for(int y = 0; y < worldHeight; y++)
            {
                for(int x = 0; x < worldWidth; x++)
                {
                    // randomizes only the top layer
                    if (y == worldHeight - 1 && Random.Range(0, 100) < 50) continue;

                    // randomizes the top two layers
                    if (y >= worldHeight - 2 && Random.Range(0, 100) < 50) continue;


                    Vector3 pos = new Vector3(x, y, z);
                    GameObject cube = GameObject.Instantiate(block, pos, Quaternion.identity);
                    cube.name = x + "_" + y + "_" + z;

                    /* My solution
                    if(y == 0)
                    {
                        Vector3 pos = new Vector3(x, y, z);
                        GameObject cube = GameObject.Instantiate(block, pos, Quaternion.identity);
                        cube.name = x + "_" + y + "_" + z;
                    }
                    else if(Random.Range(0, 2) == 1 && y > 0)
                    {
                        Vector3 pos = new Vector3(x, y, z);
                        GameObject cube = GameObject.Instantiate(block, pos, Quaternion.identity);
                        cube.name = x + "_" + y + "_" + z;
                    }
                    */

                }
                yield return null;
            }
    }


    // Start is called before the first frame update
    void Start()
    {
        StartCoroutine(BuildWorld());
    }

    // Update is called once per frame
    void Update()
    {
        
    }
}