If you’ve been paying attention, you might have heard of Destiny – the latest game from the folks who created the blockbuster Halo series. Oh, you’ve not heard of that either? Um, ok, well put it this way: it’s a video game that cost a rumored $500 million to make.

Now, as product folks, we know a budget like that doesn’t come without a rock solid guarantee of a sizeable return, so it’s no surprise that at every turn as I’ve been playing Destiny, I’ve noticed elements of engaging SaaS product design, aimed at increasing my investment and time spent with the game.

The critical reception has varied, but one thing that’s undeniable is how addictive Destiny is, and I’m far from alone in thinking so. A quick search will turn up a loud consensus: that although the game is severely flawed in certain aspects, even some of its biggest detractors are having a hard time pulling away from it. So I decided to do a teardown of Destiny’s game mechanics, to see what I could learn about building a habit-forming software product.


What is Destiny?

The premise of the game is pretty simple:

  1. Aliens threaten humanity, so you need to shoot them until they’re all gone – and there are a lot of them
  2. The more you play, the tougher your enemies get, but your character also becomes more experienced
  3. Building up your experience and reputation allows you to access better weapons, armor, and accessories, which enable you to take on tougher foes

If you’re blinking dumbly right now and thinking this sounds like pretty much every video game’s premise since the dawn of Space Invaders, you’re right. So what makes Destiny so uniquely addictive?

To answer this, I’m going to apply two theories relevant to how addictive products are made: the Zeigarnik Effect, named after Russian psychologist Bluma Zeigarnik, and the Hooked Model, created by authors and entrepreneurs Nir Eyal and Ryan Hoover.

The Zeigarnik Effect

We’ve talked about the Zeigarnik effect before as it pertains to driving deep user engagement, so it’s no surprise to be seeing it surfacing in an addictive game too.

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In 1927 Zeigarnik discovered that incomplete or interrupted tasks are remembered better than completed tasks – they create an itch in your brain that needs to be scratched – what’s now known as the Zeigarnik Effect. Examples of the effect in action include:

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I dunno about you, but my skin feels like there are bugs crawling all over me right now just from writing those things – so you get the picture.

How Destiny Applies the Zeigarnik Effect

Destiny’s very model is architected to tap deeply into the Zeigarnik Effect with its players – there’s always something that’s incomplete in the game, whether it’s being able to afford that more powerful weapon, or that set of armor that’s just out of reach of your character, or special missions in the game that you must be above a certain level of accomplishment to access.

Destiny uses two specific techniques for harnessing the Zeigarnik effect to maintain players’ engagement:

1. Completeness Meters

There are completeness meters everywhere in Destiny! First off, you’re constantly shown your current level and progression required to reach the next level – whenever you level up, the experience bar empties, and it must be filled again.


The game has several factions that you must curry favor with in order to earn the most powerful upgrades in the game.


Speaking of upgrades, your weapons, armor, and abilities can be upgraded by constant use which grant special abilities, but these upgrades are – yup, meters that must be filled, and sit there, incomplete, and begging to be filled via repeated play sessions.


2. Scoring (Leveling Up)

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Scoring is a form of social proof, or validation in the eyes of others (hey, guess what, we’ve written about designing for social proof too ;), and it’s strongly leveraged in Destiny. All players are measured by a level, starting at 1 and capping out at level 30. The higher your level, the stronger your character is, and the more ambitious missions you can attempt to accomplish for greater rewards, and so on.

By locking away the most desirable rewards and best content away for all except those who reach a certain level, Bungie, the development team behind Destiny, is relying on players’ innate competitiveness to push them into repeated play sessions. In fact, it’s scoring systems like this that we’re using as models for our own product Filament – using a score to motivate our users to continually improve the engagement of their blogs.

The Hook Model

In their excellent book “Hooked”, Nir Eyal and Ryan Hoover break down the most addictive SaaS products on the planet to explain what’s made them so compelling to so many people. The Hook Canvas is the model they’ve created to explain this cycle.

The Hook Canvas consists of four phases of a continuous loop:


The theory says that these four stages of the Hook form a continuous and escalating loop of user engagement – put simply, together they create a habit-forming product.

Applying the Hooked Model to Destiny

Destiny’s mechanics and incentives structure tightly aligns with the four steps of the Hook Model.

Internal & External Triggers


Remember, Actions in the Hook Model are defined as the “Simplest action in anticipation of a reward” – which in Destiny’s case translates to shoot all the things.


Performing said shooting is motivated in part by camaraderie, or rather acceptance by your peers who also play the game (Dr. BJ Fogg, Stanford). No-one wants to be looking shabby in comparison to their friends, which is why there’s an extensive part of the game built around equipping & customizing the weapons & armor you wear into battle, to show off to other players.

Variable Reward

The nucleus accumbens is the part of our brain that’s active when we crave something. When activated, it stimulates pleasure in the form of anticipation, and becomes calmed when it gets what was craved. In addition, the nucleus accumbens is highly stimulated by variability, or uncertain outcomes.

Destiny is layered, no, littered with variable reward patterns! Check it out:

I could go on.

Destiny uses multiple systems to tease our brain’s pleasure center with anticipation of a reward, combined with activating our nucleus accumbens by making the reward variable at every level. It’s essentially commandeering players’ anticipation – whether it’s getting loot, exchanging Engrams, or what-have-you – and using it as an itch to motivate just one more play.

Our feeble brains’ pleasure centers never stood a chance.


Investment is what happens when users are asked to do something in anticipation of future benefits. They serve two functions in the Hook model:

  1. They load the trigger to begin the next Hook cycle, and
  2. Add more value to the product, increasing the motivation to proceed with another cycle

This is the mechanism that raises the stakes and creates the escalating need to continually use the product. The more they play, the higher the stakes.

The Investment mechanism in Destiny takes the form of leveling up, which grants rewards in the form of:

We value things more when we put work into them – this is why levelling up is known colloquially as “grinding”. A glance at the Destiny community forums will reveal constant complaints about the need for undertaking repetitive “grinding” activities, yet there’s also a certain shared pride in the amount of work needed to reach a high level. Hey, grinding even sounds like grim determination.

So it’s pretty clear that Destiny’s mechanics fit neatly into the Hooked model. But let’s take a look at what happened when the Hook Model worked perhaps a little too well.

When Hooks Go Wrong: Loot Caves & Unintended User Behavior

On September 20th, 2014, well-known gaming site Kotaku published an article titled “Why High-Level Destiny Players Are All Shooting At The Same Cave”, highlighting a spot in the world where new enemies were constantly entering the game area in tight groups that could be quickly and easily killed, and the rewards they dropped harvested.

Players began assembling in large groups at the same spot (now dubbed the “Loot Cave”) and spending hours repeatedly shooting at the Loot Cave to farm rewards and gear – instead of playing the game! As one reviewer noted:

“The pull of the slot machines may be strong, but this casino has a hell of a dance floor.” – Joe Goulcher

The result was that players could quickly amass more items and progress faster by shooting the infinite stream of enemies coming out of one cave on one planet, than by doing the actual missions the game laid out for them across the entire solar system.

And why not? After all, each of the elements for an addictive Hook were there – players had just found a shortcut to get to the rewards faster.

The Trigger – desire for faster progression

The Action – Here’s where things got tripped up. Remember how we defined the Action earlier?

“Action = Simplest action in anticipation of a reward”

Doing missions to get rewards takes time, but at the loot cave, you didn’t have to do all the running around, chasing down enemies – they came out in tight groups that could be effortlessly felled over and over again, for as long as the player could stand the repetition.


The Reward – Enemies downed at the Loot Cave frequently dropped loot, which quickly accumulated in large amounts & could be traded for – you guessed it – a variable reward of weapons and armor, which caused players to increase…

The Investment – With better armor and gear, they progressed closer to the exclusive content in the game.

You see where I’m headed with this? Blasting away at the Loot Cave had become the new and unintended Simplest Action – it’s as if you discovered an easy way to pull the slot machine lever hundreds of times per minute.

The existence of the loot cave gave players a shortcut to the rewards they craved, and boy, did they take it – the Loot Cave was partially credited for driving Destiny to reach 3.2 million daily players in its first month, with an average play time of around 3hrs, even on weekdays! (source)

For a couple of weeks after the Loot Cave’s discovery, Destiny in effect became the most expensive and addictive slot machine in history – which is probably why Bungie promptly patched it out of the game in their very first update.

Summing It All Up – Using Psychology To Build Habit-Forming Products

Destiny is a deliberately engineered piece of software that has successfully applied human psychological theories such as the Zeigarnik Effect and the Hook Model to encourage sustained engagement with it – even among users who are openly frustrated with it!

There’s not a startup around that wouldn’t want this kind of user engagement, so Destiny has kindly provided some key takeaways for us all:

Internally, we’re applying these findings to our own product, Filament, which is a blog analytics and plugin platform that’ll help anyone who wants to grow a more engaged audience – because as UX fanatics, we want everyone to be able to level up their blog’s engagement!

Ok, now it’s your turn: how will you make your product or website more engaging? For some great inspiration be sure to check out The Complete Guide to the Product Design Process we have put together.