iPad app - Submission to app store

Is it necessary to make my app work in both orientations "Landscape" and "Portrait" so that apple won't reject the 开发者_如何学JAVAapp? I'm planning to create my app that works only in landscope mode. Can I do this?

If it works in Landscape, it should also work in landscape upside-down. Same with the portrait and portrait upside-down pair. I have seen iPad apps that only work in 2 of the 4 orientations, as per the above, accepted into the App store, because that makes sense for the app (example: a piano app which only displays the keyboard the long way across the display, etc.)

I have several apps that only work in one or other orientation, whilst not encouraged, it's not an automatic fail