Enhance Tutorial

[nikeee]

Via HN:

Looks cool, but either the default graph has incorrect comments, or it's buggy on firefox. There were no lightbulbs, and clicking on "a" did nothing.

It actually depends on the cursor location if the light bulb will appear. |a shows a lightbulb while a| not. This is due to the current pattern matching implementation.

Also, the initial light bulb (that should show the ability to refactor the graph, as the default cursor location is 0,0) does not seem to be visible. It should look like this:

Maybe relying on the default cursor location is not what we want here.