hi! i am looking for a great flight simulator for iOS recently, and founded x-plane the best choice. the x-plane app is both available for the iPhone and the iPad, but their description is different. so, i wonder if there is difference between them. the size is the same, and the version is the same, but it doesn't have the "+" mark on the price tag. can i purchase the iPad version and download it on my iPhone for no additional cost? thanks