local EMain =game.StarterGui.Energy.Holder.EMain **--here are the variables**
local Bar = game.StarterGui.Energy.Holder.EBar
local UIS = game:GetService("UserInputService")
local Energy = 3

print(Energy)

UIS.InputBegan:Connect(function(key)
    if key.KeyCode == Enum.KeyCode.LeftShift then
        if Energy > 0 then
            Energy = Energy - 1
            print(Energy)
        end
    end
end)

while true do
    wait()
    if Energy == 3 then
        Bar.Size = UDim2.new(0, 100, 0, 100) **--change the size**
    elseif Energy == 2 then
        Bar.Size = UDim2.new(0, 80, 0, 80)
    elseif Energy == 1 then
        Bar.Size = UDim2.new(0, 60, 0, 60)
    elseif Energy == 0 then
        Bar.Size = UDim2.new(0, 40, 0, 40)
    end
end **--it didn't show any errors so I don't know what went wrong

**
while true do
wait()
if Energy < 3 then
wait(2)
Energy = Energy + 1
print(Energy)
end
end

I tried to loop it but it still didn’t work