To me it’s ok, even though it was clever enough not to be evident at first sight. I had to remove the styles one by one and I only noticed the opacity at the very last moment, that’s like the sun shining in my face suddenly, you know (: The rest was just evidence, work and fine tuning.
However, for others it can be much less evident/easy. I wish I had time to deconstruct it and make a step-by-step on my sandbox, it’s worth it because it seems to work flawlessly (let aside the modile behavior). If one day you have time to make a tuto on that i’m sure it will be a successful one.
For now I don’t see one. I’d hide the form alltogether for handsets and craft a dedicated one only for these devices.