Ironically, flat UI MAY have made this problem more difficult to solve. Imagine if we were still on some sort of skeumorphism design on iOS, then we MAY be able

Ironically, flat UI MAY have made this problem more difficult to solve. Imagine if we were still on some sort of skeumorphism design on iOS, then we MAY be able to come up with some sort of layer/depth/texture visual hint that makes people want to press one area harder. I have no idea what that would look like, but on a random note, a bubble wrap popping game with 3D touch support would be dope.