New TransitionScript (LocalScript)

local Transition = script.Parent.Transition

Transition.Size = UDim2.new(0,0,0,0)
Transition:TweenSize(UDim2.new(0,0,0,0))

wait(3)

Transition:TweenSize(UDim2.new(1,0,1,0))

while true do
    Transition.ImageRectOffset = Vector2.new(1,0)
    wait(1)
    Transition.ImageRectOffset = Vector2.new(0,0)
    wait(1)
    Transition.ImageRectOffset = Vector2.new(1,0)
    wait(1)
    Transition.ImageRectOffset = Vector2.new(0,0)
    wait(1)
    Transition.ImageRectOffset = Vector2.new(1,0)
    wait(1)
    Transition.ImageRectOffset = Vector2.new(0,0)
    wait(1)
    break
end

wait(5)
Transition.GameLogo:TweenSize(UDim2.new(0,0,0,0))
wait(3)
Transition:TweenSize(UDim2.new(0,0,0,0))