During Build 2014, I ported over the Fall Fury game, that was originally written for Windows Store using DirectX. Porting it over to a Universal app was quite an experience. The game would compile and work on Windows just fine but as soon as I put Windows Phone 8.1 in the mix, things started going haywire. The resolution was askew, the items were going off screen etc. It took quite a bit of working but eventually, I managed to fix the game so it would run fine on the 1080p phone. There are some resolution gotchas that I could not get around to before I ran out of time.
Anyways, if you want to play around with it, I published the source for the Universal App on github for you to check out.