If anyone's stuck on hard mode, use the cross eye technique. Cross your eyes to make the two pictures merge into one picture. The differences are much easier to pick out when you do this!
I actually managed to finish it with a trackpad XD I am so happy. Although, if I am honest, the game wasn't *that* difficult to complete with a trackpad. Certainly I've come across games that feel nigh on impossible to complete with a trackpad, and this wasn't one of them. But I really loved the concept, so 5 stars from me!
I return to this game and they've neutered Memory Map in Cloud City :( Before you had to get the coins in the green boxes; so some of the 28 doors were useful. Now there are no coins in any green boxes, so now only one of the 28 doors is actually relevant! How confusing this must be to a new player; 27 doors that serve absolutely no purpose whatsoever...
 "Innkeeper"){kind=icon}
 "Coinbox Hero"){kind=icon}
 "Moonlight Differences"){kind=icon}
 "Experimental Shooter"){kind=icon}
 "Boss Battle"){kind=icon}
 "Hello Worlds!"){kind=icon}
 "Insectonator: Zombie mode"){kind=icon}
 "Space is Key"){kind=icon}
 "Red Remover"){kind=icon}