Aside from one puzzle that had me scratching my head, the only part that made me want to give up was the first half or so of Chapter 5. I was playing on Easy, albeit, but I didn't have trouble with anything aside from my own general stupidity.
Got this despite all the bad reviews and I'm mostly not disappointed. I would've liked to see some more powers for Amy, and maybe a bit longer since - once you know what you're doing - the levels are extremely short. But for a ten dollar arcade game? It's pretty boss overall.