These declarations can go in the .panel-content rule nested in #panel-donate.
But moreover, I think we can follow the standard padding <code>20px 20px 20px 40%</code> combined with the inline-block labels so the %50 option will wrap. That also means the expanded text can line up with the collapsed title and we don't have to move the background horizontally (which looks weird when it moves in two directions on expansion). Wrapping labels around the inputs lets us fix a multitude of things. Win!