Not so much a question, read on

Just noticed that there is a usability issue in this, the top three input buttons have areas where you can't click on them. The problem is coming from the 80px padding of the paragraph above it.

Because the input buttons are display: inline by default, they aren't recognising that pattern anyway, and if it was recognising it, then the space would look quite weird.

In the following rule:

#answers p {
  max-width: 760px;
  margin: auto;
  padding: 80px 0;
}

I changed the top and bottom padding to 50px, i.e:

#answers p {
  max-width: 760px;
  margin: auto;
  padding: 50px 0;
}

This way the top three input boxes are not obscured. Without doing this the only way to fill out all the inputs is through using the tab key. So it's a slight accessibility issue, through ironic in that it isn't for people who can't use a mouse, but can't use a keyboard!

The left and right input buttons can be clicked partially, because the padding does not extend to the edges. Interestingly the margin does not seem to effect the click-ability of the input, only the padding.

You may be able to change this, to improve the experience for future people.

Cheers