How would I go about stopping entity from flying everywhere?

I am making a butterfly that flies around randomly. My issue is that the butterfly keeps on flying through the floor and disappearing. I was wondering if there was a way to restrict the area the butterfly can fly in. Here is my script

local Body = script.Parent.PrimaryPart

function move()
    for i = 1, 21 do
            script.Parent:SetPrimaryPartCFrame(Body.CFrame*CFrame.Angles(math.rad(math.random(-5,5)), math.rad(math.random(-5,5)), math.rad(math.random(-5,5))))
        wait()
        script.Parent:SetPrimaryPartCFrame(Hinge.CFrame*CFrame.new(1,0,0))
        end
end


while true do
    move()
end

If anyone has a way to stop it from flying everywhere or any resources I could use, that would be amazing.