contrast, like a photo negative. Your app should be easy to read with this set- ting both on and off.) · Be frugal with fonts. Standard iPhone Helvetica fits the bill in nearly every case; stifle the instinct to stray to other typefaces. The navigation bar in par- ticular is sacrosanct: with the exception of logo graphics, always use Helvetica for screen titles. The navigation bar is such a fundamental part of the inter- face that it feels like part of the overall iPhone system; consistent use of the Helvetica system font is always the right thing to do there. Elsewhere, using a different sans-serif font (Arial, Verdana, or Trebuchet) in place of Helvetica just feels weird on the iPhone; a lateral shift that succeeds only in making your app seem like it's not a proper iPhone citizen. Changes to more boldly different typefaces, however, can be appropriate under specific circumstances. Serif fonts (Georgia or Times) work well for displaying long-form text like news articles or ebooks, giving apps a stately, traditional feel. Marker Felt, the iPhone's faux handwriting font, is just fine for notepad and grocery-list apps when you want to display users' personal notes in a casual scrawl. Just know that Marker Felt, like most script typefaces, can give your app a kindergarten feel that might not fit the personality you're after. That didn't stop Apple from