In darts, hitting the bulls-eye is harder to do than hitting any other part of the dartboard. This is because the bullseye is the smallest target. This same principle can also apply to touch targets on mobile devices. Smaller touch targets are harder for users to hit than larger ones. When you’re designing mobile interfaces, it’s best to make your targets big so that they’re easy for users to tap. But exactly how big should you make them to give the best...