Gacha example

About this model

This diagram models a loot drop system with varying rarity levels for items, featuring mechanics that simulate the probabilities of obtaining items of different rarities - Common, Rare, and Legendary. In this system, each roll has predetermined probabilities to yield an item from one of these categories. Specifically, there is a base chance for each category (the majority being Common items with the highest chance, followed by Rare, and with Legendary items being the least probable).

Additionally, the system incorporates a mechanism to adjust the probability of acquiring a Legendary item based on the number of rolls since the last Legendary item was obtained. This is implemented through a counter that increments with each roll and, upon reaching a threshold (25 rolls without a Legendary item), triggers a significant increase in the chance of the next roll producing a Legendary item. This adjustment is dynamically managed by monitoring the loot distribution, effectively ensuring that the longer players go without discovering a Legendary item, the higher their chances become of receiving one, thereby preventing prolonged streaks of bad luck.

This public Machinations diagram, “Gacha example”, was shared in the Machinations Community by Jim Stenman.

You can open the original diagram in the Machinations app, press Play to watch how resources move through it, and change its values to see how the system responds. Machinations is a visual tool for designing, simulating and balancing game economies and other systems, where resources flow through sources, pools, drains, converters and gates. In a diagram, a source creates resources, a pool stores them, a drain removes them, a converter changes one resource into another and a gate decides where they go next.