Totally agree with you there, a demo would be great, but the main point of the Android version having a demo at all, rather than there being no demos, is so that android players can check if their device will run/support the game, since that's often a problem for mobile play.
And, well, you didn't hear it from me, but certain websites can get you a free version if you want to try before you buy. That's what I did, because this dev deserves the monetary support for this quality of a game.