Solution to your Issue

math.random will return any number between a,b. Therefore it can return decimal numbers too. you can use math.ceil to get either expected number. (math.ceil rounds upwards.)

Randomly selecting a Part

This is very simple. You can place all Bricks into a Table, and randomly selecting the Element. First and foremost you’ll reference the Parts and set them up. Like so:

local Parts = {workspace.Part1,workspace.Part2,workspace.Part3}

This is Table, if you didn’t know already. It allows you to set two or more values in a single variable.

Then, we will use said math.random to select a random Element in Parts. As Tables use numerical indexing to reference each Element.

math.randomseed(tick()) -- increase actual randomization
local RandomPart = Parts[math.random(1,#Parts)]

As you know, math.random returns any number between a,b. Square brackets are used to index an Element. For example Parts[2] would be Part2. We can use math.random to give us a random index in Parts. For us to properly do so, you’ll have to give it 1, as the lowest index, and #Parts, which will return the total length of Parts, which will be the highest; last.

After we’ve got our randomly selected Part: RandomPart, you can run it through whichever transparency function you’ve written.

Hope this is what you’re looking for! If so, don’t forget to accept!