game – Spawning random small cubes in a big invisible cube using Unity C#

My goal was to create a big invisible cube and inside that spawn small random cubes.

These small cubes would have:

• A random position within the big cube.
• A random colour.
• A random size.
• A random lifetime.
• A higher chance to spawn with offset of 0 on y-axis than any other
  offset.
• Ability to rotate in sync with the big cube.
• Ability to fade away as it ages.
• To be replaced with new random cubes as they expire.

To achieve this, here is the code I wrote:

SpawnCube.cs

    public GameObject smallCubePrefab;
    public float rateOfSpawn = 1;
    private float nextSpawn = 0;

    // Update is called once per frame
    void Update()
    {
        // Spawn new cubes at specified spawn rate
        if (Time.time > nextSpawn)
        {
            nextSpawn = Time.time + rateOfSpawn;
            StartCoroutine(FadeOutCube());
        }
    }

    public List<GameObject> SpawnSmallCubes()
    {
        // Create an empty list of cubes
        List<GameObject> cubesList = new List<GameObject>();

        // Spawn cube at random position within the big cube's transform position
        Vector3 randPosition = new Vector3(Random.Range(-1f, 1f), 0, Random.Range(-1f, 1f));

        // Generate higher chance (2 chances in 3) of spawning small cubes with offset = 0 on Y-axis 
        List<float> randomY = new List<float>() {0, 0, Random.Range(-1f, 1f)};
        randPosition.y = randomY(Random.Range(0, 3));
        randPosition = transform.TransformPoint(randPosition * .5f);

        // Spawn small cube
        GameObject smallCube = Instantiate(smallCubePrefab, randPosition, transform.rotation);

        // Give random color
        smallCube.GetComponent<Renderer>().material.color = Random.ColorHSV(0f, 1f, 1f, 1f, 0.5f, 1f);

        // Give random size
        int randSize = Random.Range(1, 10);
        smallCube.transform.localScale = new Vector3(randSize, randSize, randSize);

        // Add spawned cube to the list of cubes
        cubesList.Add(smallCube);

        return cubesList;
    }

    public IEnumerator FadeOutCube()
    {
        // Give random lifetime
        float fadeSpeed = Random.Range(0.01f, 0.05f);
 
        List<GameObject> smallCubes = SpawnSmallCubes();

        foreach (GameObject cube in smallCubes.ToArray())
        {
            while (cube.GetComponent<Renderer>().material.color.a > 0)
            {
                Color cubeColor = cube.GetComponent<Renderer>().material.color;
                float fadeAmount = cubeColor.a - (fadeSpeed * Time.deltaTime);

                cubeColor = new Color(cubeColor.r, cubeColor.g, cubeColor.b, fadeAmount);
                cube.GetComponent<Renderer>().material.color = cubeColor;
                yield return null;
            }
            if(cube.GetComponent<Renderer>().material.color.a <= 0)
            {
                Destroy(cube);
                smallCubes.Remove(cube);
            }
        }
    }  

Rotate.cs

public Vector3 rotationSpeed;

    // Update is called once per frame
    void Update()
    {
        transform.Rotate(rotationSpeed * Time.deltaTime);
    }

Any suggestions for improvement or changes to make it better in any way?

Thanks