kame

https://github.com/andypike/kame

Kame (Japanese for turtle) is an implementation of the Logo programming language built as a challenge to myself. I wanted a simple way to introduce programming in Ruby to my daughter and thought this would be fun. With Kame, you control the movement of a turtle around the screen by programming commands. With these simple commands your turtle will draw you a picture. It's a nice introduction to programming for kids and will also help their maths :o)