Using multiple stylesheets with pixate, for iOS specific styles.

_ios_seven.scss

// _ios_seven.scss
// iOS 7 specific styles

app_delegate.rb

class AppDelegate
  def application(application, didFinishLaunchingWithOptions:launchOptions)
    stylesheet = (Device.ios_version.to_f >= 7.0) ? 'ios_seven.css' : 'default.css'
    PXEngine.styleSheetFromFilePath(File.join(NSBundle.mainBundle.resourcePath, stylesheet), withOrigin:0)
    true
  end
end

default.scss

// default.scss
@import 'main'

ios_seven.scss

// ios_seven.scss
@import 'main';
@import 'ios_seven';