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  • Solving Luck Manipulation In Roguelike Design

    [10.29.20]
    - Alex Pine

  • Fight fire with fire

    Now, hold on a second there, this might seem a little counter-intuitive, but yes, we can combat RNG abuse by having more RNG.

    It's a strange choice, for sure, but let me give you a little example to illustrate. Let's say we roll a single die, and we visualise the different probabilities. It's pretty flat and simple, with each of the probabilities being at 1/6.

    Here, I made a graph! The x axis is the different numbers you could get on the die, and the y axis is the probability of that happening - they're all at 1/6.

    Now, if we roll two dice and take their sum, we can see that the probability is higher towards the middle values, and very high or very low values are less common.

    The chance of landing in that 6-8 region is almost 50%, but the chance of landing on the extreme ends is just above 5%. This is part of why many table-tops will use 2d6 instead of 1d12 for many rolls, even though the range of possible values is very similar.

    Combinatorics tells us that if we roll more dice, the probability curve gets a pointier peak in the middle. And this is super important - the more dice we roll, the less likely it becomes that we get extreme scenarios.

    Here's probability distribution for 10 dice - results close to 10 or 60 are so rare they're almost impossible.

    And, strange as it may seem, this approach can work in roguelikes, too, in a bizarre fashion. Essentially, if we have more RNG, especially more items, then the probability of extremely powerful or extremely unlucky runs will be smaller.

    This is a very strange, although a very fresh approach to the problem. I've only seen one franchise pull something like this off - perhaps not intentionally for this purpose - and it's the Risk of Rain games. Whereas most roguelikes will go with 5-10 stages and something around 3-5 items per stage, the Risk of Rain games will have around 10-20 items per stage. The flow of progression is so rapid that you won't really have a reason to ever reset your runs. There's the fact that extremely good or extremely bad runs hardly ever happen - and why even abuse RNG when there's a heap of more items just seconds away?

    As soon as you get past the first few stages, Risk of Rain showers you with a stream of items, so there's no reason to abuse RNG

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