I bought it months ago (I think when it was part of the $0.10 app deals?) from the Android store. Its ideally played with something with buttons, though touch doesn't work so bad if you're just playing casually.
Does the Amazon app store still run in the background and use up data/battery when you're using an app you got from it? I've stayed away from the Amazon store since finding that out (although the deals have been pretty awful as of late anyway). Has that changed?