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  • Solving Luck Manipulation In Roguelike Design

    [10.29.20]
    - Alex Pine

  • Weighted RNG + feedback loops

    One neat thing about RNG is that, unlike with a dice roll, the players don't get to see the number generation process - only the result. The downside of this is that humans tend to be a bit stupid when it comes to mathematics, and many games have to lie about how their RNG works to prevent players from getting frustrated by numbers not aligning up with their warped perception of random chance. The upside is that we can pull off all sorts of weird trickery behind the curtains and players won't even notice. It's like politics, but not rooted in pure evil!

    With unsatisfying runs being the main cause for RNG abuse, perhaps we can manipulate RNG behind the scenes to ensure that all runs are the right amount of satisfying. RNG that doesn't follow a uniform distribution - meaning some results are more likely than others - is called weighted RNG. Combine this with affecting a player's chance of success or failure depending on how well they've been doing so far (which is also called a feedback loop in game design), and what you get is perhaps my favourite method for solving RNG abuse.

    If your player finds too many high quality items, weight the RNG to give more low quality items, and vice versa. This ensures the most satisfying amount of player strength in every run, and they won't be abusing RNG because, if you make sure the RNG is forgiving but not overly generous, they won't be incentivized to retry. I mentioned the genre having a sort of madness-generating freedom - here we control that freedom a bit to tune down the madness.

    In Half-Life 2, being at low health makes useful pickups drop more. While not related to RNG abuse, it is an example of negative feedback loops used to automatically find the right experience for the player. Fun fact: this type of negative feedback loop is called dynamic difficulty adjustment.

    Obviously, this brings in a whole heap of annoying technicalities. You need to assign some quality variable to every item (something that The Binding of Isaac would have benefited greatly from), balance to find the right amount of power, and do all the coding required to make this feedback loop work correctly. It might be a hassle, but I'd argue it's worth it, as it's perhaps the best method for disincentivising RNG abuse. While most other methods discourage the player from abusing RNG when their runs are unsatisfying, this one strikes right at the root of the problem and makes sure that runs are satisfying in the first place. Can you see how brilliant this is? And, while it may be complicated for the devs, on the player side this method is extremely elegant - they won't even notice that RNG is being manipulated. Solutions like this are what makes game design so exciting to me.

    I would love to provide some examples for games that do this well, but that's rather difficult. I can't be sure if it's because this method is used extremely rarely or because, by nature, it's really damn hard to notice when designers do this. Part of the brilliance of weighted RNG and feedback loops is that a lot of the time the player isn't even told about it - it just feels right, and you don't even think about what's creating that right. So there may already be some popular roguelikes that do this and I haven't even noticed it!

    I have seen something similar to this in Enter the Gungeon's "magnificence" system. Magnificence is a hidden stat that, if the player has a lot of high quality items, decreases the chance of finding more high quality items. And that's it! It's simple, yet one of the most clever ideas in roguelike design I've seen - I just wish more games would do this and also implement it the other way around, to make sure the player doesn't get too many low quality items.

    Increasing agency

    As we already discussed, RNG abuse happens because the player's goals are in direct conflict with the game's systems. The player wants to optimise their runs, but the RNG is in control of the progression and might hinder this goal. The player, obviously, doesn't like this, and attempts to take back agency the only way they know how - by abusing the game's RNG.

    This phrasing of the problem lets us see a new approach to solving it - perhaps we can give the players different means to have agency over their runs? If they feel like they have more influence towards how their runs will go, they won't need to resort to RNG abuse to exert control.

    This one's interesting because it's actually rather vague and you can pull it off in many different ways. However, if you do use this method, there is one thing that you definitely should keep in mind - there is such a thing as "too much" agency, especially in roguelikes. My advice is: let the player have some control, but keep the unpredictable nature of the genre.

    So, for example, Hades does this in a fairly straightforward way. Whenever you receive an upgrade or boon that strengthens your character, RNG picks three options for you and you get to choose one of them. This means the game is still unpredictable and exciting - you don't know which three options the RNG will choose - but you are given enough agency over how you progress that there's never really any need to abuse RNG.

    Hades often lets you choose one of three things picked randomly from a wider pool, thus increasing agency. Hades is also really, really good. Go play it.

    Nuclear Throne gives you a bit of agency by letting you keep "golden weapons" between runs, giving you some personalisation. For example, I love crossbows, so I always carry a golden crossbow between runs.

    Risk of Rain 2 is a little trickier. In it, you can find 3D printers that choose one of your items at random and give you another item in exchange - you know what item you'll get, you don't know what you'll lose. Furthermore, once in a while you're able to turn items of your choice into scrap, and scrap gets prioritized in 3D printers, meaning you don't need to risk losing more valuable stuff. This allows players to make more personalized builds and combats RNG abuse by increasing agency.

    Risk of Rain 2's scrappers let you personalise your runs - you can choose which items matter less and later exchange them for more powerful gear

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