With more than 50 million copies of Rovio's bird-slinging casual game downloaded, Angry Birds is one of the most popular games of all time, but why? Usability engineering consultant Charles Mauro tears down the surprising secrets to Angry Birds' success.
A certified human factors engineering professional and president of usability engineering and user interface design consulting firm MauroNewMedia, Charles L. Mauro uses cognitive science every day to help software companies figure out why their clients don't find their software engaging. Questions like these are easily answered via experience and usability analysis.
It's not so simple when he is asked to determine what makes a piece of software ridiculously successful, likely being played by thousands of gamers across a handful of platforms as you read this.
In order to determine what makes a piece of software successful, Mauro has to employ cognitive reverse engineering to determine which elements of the user interface lend themselves to creating a psychologically engaging user experience.
In his deconstruction of Angry Birds, Mauro touches on many elements we were already aware of, though he presents them in a new, deeper light. For example, while the user interface of the game seems quite simple, it's the way the game slowly introduces the player to new concepts that keeps the game from growing stale.
What makes a user interface engaging is adding more detail to the user's mental model at just the right time. Angry Birds' simple interaction model is easy to learn because it allows the user to quickly develop a mental model of the game's interaction methodology, core strategy and scoring processes. It is engaging, in fact addictive, due to the carefully scripted expansion of the user's mental model of the strategy component and incremental increases in problem/solution methodology. These little birds are packed with clever behaviours that expand the user's mental model at just the point when game-level complexity is increased.
Mauro then moves on to the game's response time, revealing a fact that not many interface designers are hip to: Faster is not always better. One would think lightning-fast reaction times are always better than pauses, but pausing in the right place at the right time is an art.
In Angry Birds game play the pigs also take a long time to expire once their houses are sent to bits. In many play sequences, seconds are consumed as the pigs teeter, slide and roll off planks or are crushed under slow falling debris. This response time of 3-5 seconds, in most user interfaces, brings users to the point of exasperation, but not with Angry Birds. Again, really smart response time management gives the user time to relax and think about how lame they are compared to their 4 year old who is already at the 26th level. It also gives the user time to structure an error correction strategy (more arc, more speed, better strategy) to improve performance on the next shot. The bottom line on how Angry Birds manages response time: fast is good, clever is better.
Mauro takes into account factors that are generally invisible to the end user. More fascinating still is the notion of manipulating short-term memory loss in order to create a game that's more compelling without becoming frustrating. The simple act of panning from a level's pig structure over to the cackling birds, awaiting their chance to give their lives for a handful of eggs, is a subtle manipulation of short-term memory.
Predictably, the user scrolls the interface back to the right to get another look at the structure. The game allows the user to reload short-term memory easily and quickly. Watch almost anyone play Angry Birds and you see this behaviour repeated time and again.
It's one of the most comprehensive usability teardowns of a game I've ever read, touching on the more elusive aspects of success like mystery (why do those bananas randomly show up on certain levels) to the more easily recognised, like sound and visual design.
It's the sort of article that makes the buried game designer deep inside me burrow a little deeper, now acutely aware of factors of design that I never even considered.
While I wallow in self-pity, I leave you Mauro's final words.
We are left with the notion that a cognitive teardown of a truly compelling user experience is vastly more interesting and insightful than simply answering the opposite question: why is a given user interface dysfunctional? To summarize, in the context of Angry Birds, success is bound up in slowing down that which could be fast, erasing that which is easily renewable, and making visual that which is mysterious and memorable. Over the past 10 years, our firm has conducted user engagement studies on hundreds of user interfaces. The vast number did not get one principle right, much less six. You go Birds! Your success certainly makes other Angry and envious.