I think it's a playground in the best sense of the term. Take some time and actually play with it, and a lot of fun stuff happens, lightbulbs go off, etc.
If you're expecting a lesson, you'll likely be disappointed, but I think there's real value in a true playground.
I think the biggest improvement would be if, when hovering over a 'neuron', you get a visual representation of what feeds into it.
For me in Chrome on OSX you do get a visual representation of the neuron's input when hovering. It shows up behind the data points in place of the neurons' output when hovering.
