Any avid reader of hacker news probably came across the sliding puzzle game 2048. If you didn't, then you probably heard of 'Threes' which was the original (iOS only at the time) inspiration for what became 2048. Since then there have been thousands of clones of the genre, some by just changing the tiles to a different theme and others tweaking the gameplay slightly or adding some polish. Either way, wherever you stand on the argument of which is better, the original threes or the 1024/2048 route, they were both great timewasters that were easy to learn but difficult to get to the big numbers. (I personally lost a lot of time to trying to reach the 2048 tile over a few weeks and various versions ranging from Dr. Who edition, numberwang edition to an animated boobs edition (mainly thanks to the usvsth3m 2048 builder ;) )