Bootstrap是否有一些技巧来定义桌面，平板电脑和手机，而不是普通的屏幕尺寸？

I've been trying to optimize my lay out as responsive as possible, but I've bumped into weird problem; despite my iPhone and iPad Mini are showing to be two different sized platforms according Bootstraps' site, yet while making edits on my lay out, they both seem to interpret the lay out in sm-size. I've been trying to optimize my lay out as resp