Some personal notes on slot machine design. With commentary about how this is/can be applied to game design. If I say that a game is designed like a slot machine, that doesn't mean that developers intentionally sat there and thought about it in those terms - oftentimes these design choices are intuitive.
Game design is fundamentally about tricking our dumb brains into viewing meaningless crap as rewarding, so gambling design emerges naturally - it's games with only the brain hacks and none of the meaning. Nothing is safe from this kind of design, and distinctions between more pure, meaningful games and addiction machines are subtle and require a whole bunch of thinking. So it's worth looking at exactly what's going on with gambling, and then later the cesspools of gacha & "hybrid casual" trash and their wonderful unique quirks & innovations, mostly to do with a sense of ownership, tedium-as-punishment & FOMO.
I'm generally going to order these by their importance to me personally.
- In Gambling, Anticipation Is Everything
Gambling isn't extrinsic or goal-oriented exactly, even though the extrinsic rewards get people hooked initially. Something that keeps popping up among particularly addicted gamblers is that they don't play for the win, they play for the anticipation. Specific, discrete goals are poisonous to this process because they create walls that stop the flow & force the players to reflect. Players report getting annoyed when they win, even.
Slot machine designers ramp up the feeling of anticipation with deliberately programmed "near misses" (showing similar-looking symbols to make people think they're close to winning, having the slot slow down in between the winning number and a losing one, etc), slow-ish rotation speed, numbers being shown one-by-one and slowing down as the final number's decided.
In games, emphasis on anticipation (without meaning) manifests in a lot of ways - animations where numbers slowly tick up and meters slowly fill in, lengthy animations/cutscenes when opening chests (Zelda's famous for this), extra layers in between an item's discovery and identifying its stats, and other stuff in that vein.
- Empty Flow State Is The Goal
"Vicarious Game-Like Experience", as it's described. Slot machines are incredibly flow-optimized, to the point where players are pissing & shitting themselves because they're in the zone (a shockingly regular occurance). They do this by reducing friction & choice as much as possible and having an endless supply of "free" goals.
Slot machines allow instant access to games and very quick restart times (ummm based?!?!). They try to strike a balance between having long enough delays to create that compulsive anticipation loop but also restart times fast enough that people can gamble without getting bored. This lack of friction is carried over into the physical world. The casino designers value ergonomics a lot - they try to make the chairs as comfortable as possible, they create a sense of isolation when you engage with the machine (a feeling of being boxed in), they replaced the more hard to pull levers with easy ones that don't offer resistance and are in a position where you can always keep your hand on them, or buttons. They even pump pleasant aromas to make you feel nice, and oxygen to keep you awake and energized. The goal is to create an environment where your body moves almost automatically. Any resistance or decision making is a barrier.
The simplicity of the game itself also means that there are no mechanics/challenges to offer meaningful resistance. Everything is about keeping the flow going. AAA devs would be proud!
Nowadays flow-optimization is huge among game designers, so it probably doesn't take much imagination or thinking to see how these things apply to video games. Difficulty & nuanced, complex mechanics offer resistance to the player's engagement and pull them out of the game initially so games attempt to balance themselves for frictionless learning (very slow escalation of difficulty, teaching in a safe environment, etc) while adding all sorts of assists to automate controls from innocent stuff like input buffers to the complex assist systems in Dead Cells. Instant restarts in arcadey games are also a type of flow-optimization that keep you hooked via endless restarts. High amounts of content is arguably a type of low-resistance goal and is often used as such.
- Goals Are Free
Slot machines aren't goal oriented, they are endless and the only limiting factor is time & money. You only have one static goal which is to keep rolling and retrying doesn't cost you anything. This distinguishes them from games in a very interesting way.
Imagine you're trying to get a personal best time or score - this is an ostensibly "endless" activity but the goals are not only dynamic and achievable, but they increase their cost the more you play. Early on, chasing PB's might have that gambling-like addictive quality, but the better you get at the game the more demanding, frustrating & time consuming PB's become. Eventually you will see almost nothing but failure, and thus get discouraged. Being concrete goals, PB's and such offer a nice off-ramp where you can stop and reflect on whether it's worth continuing. Many people quit once they reach their goal, or at least take a lengthy break to cool down.
A lot of content with easy goals and static-ish difficulty goes against this. It gives you a constant drip feed of goals that don't give you much resistance, as a result keeping you addicted & hooked.
- Offsetting Long Term Losses With Short Term Gains
This is what makes slot machines profitable - they make you think you're winning even as you're losing. If the machines just took your money, you would be discouraged by the loss-streaks, introducing meaningful resistance/friction back into the experience. The goal is to avoid that. This is achieved in many, many ways.
Machines are tuned to give you 80-95% of your money back (which could be adjusted on-the-fly :) the casinos would NEVER but the tech is there) which lessens the feeling of loss and allows for a lot of fun things to happen such as long win streaks. Machines added more winning/losing symbol combos because players focus on the winning combos and ignore the fact that losing combos have been increased too. Casinos give special gifts that scale proportionately to how much money you've spent in order to create the feeling that you're winning short-term.
Since games aren't really about winning/losing money, this doesn't get applied as directly to them. However there are still uses for this general principle such as RPG power scaling system. If you want players to feel like they're becoming more powerful while controlling progression via scaling, simply limit what you scale. If there's an over-abundance of weak enemies that players can flex on, they won't pay as much attention to the fact that the stronger enemies scale to their level, as long as it's not too blatant.
- Deliberately Confusing Audiovisual Feedback
Slot machines prey on your guesstimates about their probability. The symbols that show up don't represent the actual game odds because it's all handled digitally and obfuscated. Slot machine designers try to make the machines feel mechanical in order to have people make false assumptions about probability. Additionally they confuse people's pattern recongition by for example having uniform sounds that play during both losses & wins, messing with people's associations.
This can be very directly applied to gacha pulls with obscure probability. The more common use though isn't scummy - devs try to compensate for player mistakes by adding things like coyote time, input buffers & tweaking hitboxes to be forgiving.
It should be noted that fixing this isn't just a matter of showing players their actual chances - probability isn't intuitive and people are infamous for struggling to understand how it works. To battle it, developers have to directly & effectively communicate what a certain pull % means in practice, and fight people's cognitive biases.
- Ownership & Trust
Some slot machines use licensing to exploit people's trust of brands, parasocial relationships with celebs & other positive associations, similar to marketing. On top of that, a lot of machines add little empty interactivity, easter eggs, and persistent progress to try & add an element of ownership - getting you attached to a particular machine, or a particular acount. This is relatively new for slot machines and is utilized in much more disgusting ways in modern games and gacha trash, so I won't explore it too much.
- Tracking/Telemetry, Celebrating Losers
This is a particularly fucked up element of casinos, particular people (losers) are marked & tracked, and since it's all digital, machines could easily adjust themselves to fit a particular client. When you see game companies talk about dynamic difficulty & telemetry, keep this in mind.
So in summary, if you're the type of evil bastard who wants to design empty addiction-driven games that learn from slot machines, then :
- Make it heavily luck-based, reliance on skill creates the possibility of either friction or boredom.
- Focus on anticipation, make it as exciting as possible both audiovisually and mechanically. Moments of anticipation are the player's God, and the whole game should revolve around them. Build tension/release cycles within that period of anticipation, reinforce them, make the thing the player's looking forward to meaningful to hook them, ideally have it feedback into the anticipation-release cycle.
- Focus on endless free goals with no friction. Have a lot of flow-optimized content (maybe procgen) with simple repetitive goals. If you escalate difficulty too suddenly or demand too much of the player, they will think twice about getting on the hamster wheel.
- Offset long term losses with short term wins, or even short term losses with short term wins. The player failed? Soften the blow, make them feel like that failure was still worth it, and maybe reward them with a win streak right after. If the player sees a game over, instantly distract them with some unlocks or some extra resources.
Normally I don't list sources but since this is entirely about psychological/gambling industry related claims, check these out :
Natasha Dow Schull's Addiction By Design is the source of a lot of this stuff, she also did a lot of interviews/talks/etc that are quick intros
https://www.youtube.com/watch?v=ETB0x2UU6JE
https://www.youtube.com/watch?v=SuwafUaIvY0
https://www.youtube.com/watch?v=ak0HE8Y_UJY
Jimmy McGee did a great series of vids covering a lot of this stuff, and he did a nice family tree tying gaming back to the gambling industry, reinforcing that stuff like arcade design is an anomaly rather than the norm :
https://www.youtube.com/watch?v=jQIHqkudgNY
https://www.youtube.com/watch?v=1X6D39Cd34k
Various vids/talks :
https://www.youtube.com/watch?v=1W2HqF4x8Bc
https://www.youtube.com/watch?v=1B5UHZhimVQ ("Vicarious Game-Like Experience" guy)
https://www.youtube.com/watch?v=_Wb2Rddn3nk
https://www.youtube.com/watch?v=CYoQrL1hKoo
https://www.youtube.com/watch?v=JyIWQIdxaOA
A lot of casino design is itself downstream from "Designing Casinos To Dominate The Competition" by Bill Friedman, the guru as Natasha Dow Schull describes him.
