Piano goes bi-dimensional!
Just as in the beginning of the Cinema they used the Theatre language in front of the camera (which, needless to say, looks preedy odd today), in the beginning of tablets they made piano-sounding apps with piano-like interfaces.
If you ever tried to play something on one of those apps, you should have noticed that all they offer is good intentions (and, sometimes, pretty fancy screenshots).
Lattice, by Appttic, offers you just the right interface.
Check out the following video to see what we are talking about: http://www.youtube.com/watch?v=y9tIXqhBJiQ
The app allows a modal interface. You can choose to play using any of the following scales, in any key: diatonic major, ditonic minor, pentatonic major, pentatonic minor, and chromatic. You have also the option of displaying note names and intervals, which are very important for learning music theory.
IMPORTANT: Before playing Lattice, disable Multitasking Gestures in your device (in the Settings app, under the General session, turn the Multitasking Gestures switch to the off position).