"Toby Walsh at the University of NSW Australia has, as reported in New Scientist, studied a generalized version of the popular game Candy Crush Saga and found it be an NP-hard problem, indeed he suggests 'Part of its addictiveness may be that Candy Crush is a computationally hard puzzle to solve.'
His paper shows that early rounds in the game can be modeled as a collection of 'wires' transmitting information across the board, with candies forming inputs and outputs, which can be seen as equivalent to logical statements, this reduces the game to an example of a Boolean satisfiability problem which is known to be NP-complete. A similar technique has been used to show that Super Mario Brothers and Zelda are also NP-hard.
Given that people have spent millions of hours playing the game he notes 'It would be interesting to see if we can profit from the time humans spend solving Candy Crush problems, perhaps we can put this to even better use by hiding some practical NP-hard problems within these puzzles?'"
Really? I thought it was a logical factor to put in to make the level more difficult. It was also innovative. That sort of thing didn't really kick in again until somewhere in the 400's where you started getting poly-colored candy (it flucuates between two colors, flipping once a move is made) but even that then generally makes for unexpected slides that generally help more than they hinder.
The hurricanes further in the 400's were somewhat annoying though, they randomly jump to anywhere on the board, delete the candy and leave a "scar" for one move which candy cannot fall into. There are a few levels with five or ten of the buggers flying around.
Having said that, I have been waiting for the last few weeks for another patch to come out so that I can continue past 530 where I am currently waiting.