Tween Model Rotation

function _G.AngleSelection(selection, rotation, a_rotation)
    local parts = {}
    local origins = {}
    local function FillSelectedParts(parent)
        for i,v in pairs(parent) do
            if #v:GetChildren() > 0 then
                FillSelectedParts(v:GetChildren())
                wait()
            end
            if v:IsA("BasePart") then
                table.insert(parts, v)
            end
        end
    end
    FillSelectedParts(selection)
    -- Gathered all the origins
    local main = parts[1]
    local frame = (rotation ~= nil and CFrame.new(main.Position) * CFrame.Angles(rotation.x, rotation.y, rotation.z) or main.CFrame * CFrame.Angles(a_rotation.x, a_rotation.y, a_rotation.z))
    for i,v in pairs(parts) do
        origins[v] = main.CFrame:toObjectSpace(v.CFrame)
    end
    --- --- --- --- ---
    -- Adjust them via main part
    for i,v in pairs(origins) do
        i.CFrame = frame:toWorldSpace(v)
    end
end
for i = 1, 90 do
    _G.AngleSelection(script.Parent:GetChildren(), nil, Vector3.new(0,0,math.rad(i)) )
    wait()
end