fortuna

Weighted gacha system.

Usage

Create an item using GachaMachine.createItem

More weight = more common

const items = [
    GachaMachine.createItem("SSR cool character", 1),
    GachaMachine.createItem("Kinda rare character", 3),
    GachaMachine.createItem("Mob character", 5),
    GachaMachine.createItem("Mob character", 5),
    GachaMachine.createItem("Mob character", 5),
  }
]

const machine = new GachaMachine(items)

machine.get(10) // Rolls 10x 

/*
    My result:
    [
      "Kinda rare character",
      "Mob character",
      "Mob character",
      "Mob character",
      "Mob character",
      "Kinda rare character",
      "Mob character",
      "Mob character",
      "Mob character",
      "Mob character"
    ]
*/

Plain weighted random selection

You probably don’t need all complicated stuff. Here’s a quick way to just create a simple weight-based gacha system: (Only works on v1.1.0 and above)

import { GachaMachine } from 'https://deno.land/x/fortuna@v1.2.0/' // wherever you are importing from. 

const items = [
    GachaMachine.createRollChoice("SSR cool character", 1),
    GachaMachine.createRollChoice("Kinda rare character", 3),
    GachaMachine.createRollChoice("Mob character", 5),
    GachaMachine.createRollChoice("Mob character", 5),
    GachaMachine.createRollChoice("Mob character", 5),
]

GachaMachine._roll(items) // Rolls one item from the list of items

Alternatively…

GachaMachine.createRollChoice just returns an object with result and chance. In otherwords, it’s useless code. Just supply your own object ez.

import { GachaMachine } from 'https://deno.land/x/fortuna@v1.2.0/' // wherever you are importing from. 

const items = [
    { result: "SSR cool character", chance: 1 },
    { result: "Kinda rare character", chance: 3 },
    { result: "Mob character", chance: 5 },
    { result: "Mob character", chance: 5 },
    { result: "Mob character", chance: 5 },
]

GachaMachine.roll(items) // Rolls one item from the list of items

Documentation

Documentation for the latest version can be found in https://doc.deno.land/https://deno.land/x/fortuna/mod.ts

A guide for usage can be found in docs.nekooftheabyss.moe

What I don’t like about fortuna atm

I initially made fortuna for a very specific purpose. When I later decided to make it an open-source, general-purpose gacha system, I had to make a lot of changes which ended up making a large part of the code look niche. More like, it is niche. The only thing a person would need from fortuna is the _roll method which I have no idea why I prefixed with an underscore.

Especially the tier and pool system. Have they ever been of use in any place? If any, those features only make the rest of the code worse. As of v1.2.0, fortuna’s earlier algorithm was replaced with a much simpler one (I realized that I was using a bunch of worthless stuff). Older algorithms can be accessed via the failures directory.

How to test a failure?

import { roll } from "https://deno.land/x/fortuna@v1.2.0/failures/roll1.ts"

You can pass an array of items of the form { result: ItemType, chance: number} where result is the value and chance is the weight of the value. ItemType is to be passed as a type parameter to roll.

So I’ll be redoing a large part of the code, mainly reworking the two features I mentioned. Hence, v2 will be coming soon with breaking changes for world peace… Hopefully. v1.2.0 is out with better typings and a better algorithm already. _roll is now roll.