Very nice!

Just one thing. I pressed the Enter key thinking that it would take me to the next step (like the right-arrow), but the page background went darker. And, each successive press of Enter made it even darker. I actually liked the effect (even if it was unintended) as it increased the contrast between the step being focused and the rest of the page.

However, I found no way to get back to original page after all the steps are completed (by right-arrow navigation). Pressing ESC had no effect.

Edit: Using Firefox 20.0 on Ubuntu Lucid.