@Gigiwoo's excellent podcast about flow has been rolling around in my head for a while now. He argues that there are three main elements (plus one anti-element) to achieving and maintaining flow: Clear Goals Feedback Balanced Difficulty No Distractions (Incidentally, Gigi, you really should put that nifty flow diagram up as a linkable image... I'd have included it here!) All makes pretty good sense, except for the third one, "Balanced Difficulty." I'd like to argue that this is missing the mark. As evidence, I point to a variety of very popular games that have essentially no difficulty at all: Cookie Clicker, Farmville, most tower/city building games, Cooper's Little Adventure, etc. So what's the real thing that keeps players engaged? I say it's accomplishment. Players must walk away feeling like they've accomplished something (however fictitious that might be). They gotta feel like this guy. Difficulty is one way to achieve that: we give players a difficult task that they can't initially do, and then hope they stick around long enough to build the skills to the point where they can do it (beat the boss, pass the level, whatever). This gives them a sense of accomplishment. But these other games show that there are much more direct ways to provide accomplishment: simply give them some clear "how they are doing" number (total cookies, cookies per second, Farmville bucks, number of fancy decorations, etc.), and make sure this increases over time. Earlier today I was generating 1000 cookies per second (cps), but now I'm making over 3000 cps; that's a morning well spent! This works even when there is essentially no difficulty or skill to the game at all; anybody can play and do the very simple interactions required to keep these numbers increasing. But there's a catch: I think people judge accomplishment in such cases by percentage change, not absolute change in the number. In the beginning, if I get my measure (whatever that is) from 10 to 11, that's a pretty decent accomplishment. Later on, if I spend the same time to get it from 1436 to 1437, that's a waste of my time. I'll go play something else. So to keep a sense of accomplishment in this case, you have to keep increasing the rate at which the numbers go up, in an exponential growth curve. Embracing this is what made Cookie Clicker so popular. When the accomplishment is dedicated toward a specific goal, such as finishing a project, then I think what we perceive is basically % complete, and % remaining. And the same effect applies: at the start of the project, we focus on % complete, and when we move that from 5% to 6%, that's noticeable and feels good. (This is true even if there is no such explicit computation, but just our own perceptions, as for example when trying to reach the end-goal in Minecraft or build a huge castle out of LEGO or whatever.) And if we get close to the end, we focus on % remaining; moving that from 5% left to 4% left also feels like a good day. But in the middle, when the best we can do in the same amount of time is go from 45% to 46% complete (or worse, from 55% to 54% left)... that's not rewarding. This is the "long slog" period that many projects (and poorly-designed games) go through, and is when we often abandon it and do something else, where the sense of accomplishment is higher. (And note that this isn't just about games — it applies in real life, too. It takes real stubbornness and discipline to get through the long slog period of any project, because the fun of accomplishment is mostly in the beginning and the end.) I believe the focus on difficulty in games is an artifact of the initial monetization scheme, i.e., chucking quarters into arcade games. Games had to be designed so that most players couldn't play them for more than a minute or two, in order to make money. And by improving their skills, players got more play per quarter, which is very rewarding (not just for the inherent accomplishment of beating a previously unbeatable challenge, but because it was linked to money — making or saving money always generates a sense of accomplishment, which leads to another great example for my thesis: slot machines!). So of course it was all about the difficulty then. But now, when that's no longer the point, I think the focus on difficulty is missing the mark. It's all about the accomplishment.