Nice simple game. I agree that a little challenge would help. I also feel like being able to rotate the camera would make it more comfortable to find the gems without compromising the hunt.
One challenge idea a friend gave me, was to make some kind of obstacle course inspired by slalom. Where you have to follow a certain path in order to receive a gem. I think that couldmake it a bit more fun.
Alright, a camera controller sounds like a nice thing to have actually :)
Thanks for playing!