A free mod for Stardew Valley, by Digus.
The Producer Framework Mod is a simple way to add new producing rules into the game. The installation process is quite simple. All you need is to download the latest version of SMAPI, unzip it to /Stardew Valley/Mods, and you are done. The rules will be automatically loaded and enabled. You can configure the settings as you see fit, but we recommend to keep it simple and just install it.
The basic concept of the app is that you can define rules for the output of an item. It is not so much of a game changer as it is a tool to help you create and build your own game.