Some work on a livecoding environment like the one in Bret Victor's talk "Inventing on Principle" at http://vimeo.com/36579366
The tree example from the talk seems to work best in Safari. (Firefox and Chrome couldn't re-render in realtime)
To run on localhost run
python -m SimpleHTTPServer
from this directory then go to http://localhost:8000
tree.js and game.js were copied from the talk and © 2012 Bret Victor