It was The Humane Environment (THE), is a very well thought out Textual and Zoomable User Interface (TUI & ZUI), implemented in Python. It's more than just a text editor, or at least it will be, see:

It is very efficient, much more so than a WIMP. For the most part, it is a recreation of the Canon Cat, which was designed by Jef Raskin as well. The difference is that The Humane Environment doesn't have the luxury of custom hardware (mostly, the keyboard, but also the mouse). This means that more of its features are not visible.

This page is linked from: The Humane Environment