How many playthroughs did it take you until you collected all gadget parts and all Knack pieces? I'm on my third playthrough and I need one more piece for one more gadget and need to unlock three more Knacks, including Diamond Knack. I keep getting pieces for the Knacks that I've already unlocked. It's frusterating.
Meowstro Edit: I've updated your thread label. More information about Labels Best Practices in PS General.
I got all of the gadget parts on my first playthrough, and all of the Knacks (except Diamond) on my second. I am now on my fifth playthrough and still only have one diamond. iOS app is useless at this point for me, I don't think you can earn diamonds from it.
:^/ I think I played though about four times before I had collected enough diamonds for Diamond Knack. After that, I used him for Hard and Very Hard modes. Interestingly, Very Hard mode wasn't really that much more challenging than Hard mode.
I learned that diamonds are not able to be copied from your friends, which feels like a cheat on the developer's part. Extended replay value should not feel forced. The player reacts to his platinum trophy with a sigh of relief, telling himself "now I don't have to do that anymore," the developer has done something wrong. A good showman always leaves the audience wanting a little bit more, instead of a lotta bit less....