RubyDung

RubyDung was an unreleased strategy game created by Notch before Minecraft, developed until Feburary 2009 at the most. Not much else is known about the game other than it is influenced by Dwarf Fortress, and that it was cancelled early in development, before it even released. Notch's next game would be Minecraft (later known as Minecraft: Java Edition), which is based on RubyDung's codebase.

About
After the game was cancelled early in development, the codebase would later be reused for Minecraft. Even grass block and cobblestone block textures that were used in this game appear in the earliest builds of Minecraft.

The grass and cobblestone textures were randomly colored on the fly. It includes a 3D texture mapper.

RubyDung inspired Notch to make Minecraft when he wanted RubyDung to have a first-person view, but when he tried making this, he thought that the textures were too blurry and distorted. Shortly after Notch's days coding for RubyDung, he came across the game Infiniminer, which put down the foundations for Minecraft.

On October 30, 2009, Notch talked about RubyDung on his blog in an entry titled "The Origins of Minecraft".

Name
The name "RubyDung" was a placeholder name for a dungeon game in the "rubylands", a rough draft of a game world by Notch.

Creation of Minecraft
Notch's inspiration for Minecraft came after he played Infiniminer. Some time later, Notch created Minecraft.

Minecraft's source code came from RubyDung, as such, the earliest versions of the game still internally refer to themselves as RubyDung.