A portion of a NintenDad interview with Goodbye Galaxy Games' Hugo Smits...

ND: The Game seems to rely on the touch screen controls. Will players be able to use the buttons as well or is the touch screen the best choice?

HS: No, basically all the input is done through the touchscreen. You can use the d-pad for camera-movement and some buttons to get back into the menu. But those buttons are also present on the screen.

The reasons for this is because of the gameplay. Thanks to the voxel engine you can destroy (or restore or build) things very precisely. The touchscreen provides a nice way to be precise in the game. For example; the wall will blow up EXACTLY where you touched it.