"Player Milking System"
It's less accurate to say "Stuck? Buy a power-up, plus some levels are almost impossible" than it is to say "Some levels are almost impossible unless and until you use a power-up". I've been stuck on some levels for days, then used a power-up I got from the Wheel and mysteriously it becomes much easier on following attempts. Dreamworld levels are especially bad for this; you get nailed again and again by huge numbers of candies from one side of the balance dropping and none from the other, then you use a power-up and suddenly you stop having three straight yellows drop to tip the owl off and you start getting neutral colours instead.