The most addictive thing that can happen to you in Candy Crush is losing a level by one move. It makes you want to play again more than actually winning does, and researchers at the University of Waterloo hooked 60 regular players up to heart rate sensors to prove it. Now watch what this guy finds when he digs through the game's code. There's a difficulty dial in there, and it turns both ways. Picture what that does to you over thousands of levels. When you're about to give up, the board gets…