Problem with while not

The problem is with:
notEnoughCrystals = false
while not notEnoughCrystals do

When I change it to:
enoughCrystals = true
while enoughCrystals do

It is working properly. Why cant I use `while not`?


Here is full code:
Settings:setCompareDimension(true, 897)

Settings:setScriptDimension(true, 897)



notEnoughEnergy = false

notEnoughCrystals = false



function notEnoughEnergy()

   return exists("notEnoughEnergy.png")

end



function refillEnergy()

   existsClick("yes.png")

   existsClick("rechargeEnergy.png")

   existsClick("yesPurchase.png")

   if exists("enough.png") then

       notEnoughCrystals = true

       toast("You have not enough crystals!")

       return false

   else

       existsClick("okPurchase.png")

       existsClick("close.png")

       return true

   end

end



function replyOnesBattle()

   existsClick("replyOnesBattle.png")

   if notEnoughEnergy() then

       if refillEnergy() then

           existsClick("replyOnesBattle.png")

       else

           return --couldnt refill energy because of no crystals

       end

   end

   startBattle()

end



function startBattle()

   existsClick("startBattle.png")

end



function waitForBattleEnd()

   while true do

       if exists("crystal.png") then

           toast("koniec")

           return

       end

       wait(1)

   end

end



function obtainBattleRewards()

   existsClick("crystal.png")

   wait(1)

   existsClick("crystal.png")

   existsClick("ok.png")

end



function playOnesBattle()

   startBattle()

   waitForBattleEnd()

   obtainBattleRewards()

end



function farm(replyBattle)

   while not notEnoughCrystals do

       playOnesBattle();

       if replyBattle then

           replyOnesBattle()

       end

   end

   toast("End of farming")

end



function notEnoughCrystals()



end



-- ========== Main ================

farm(true)