Beautiful game. The gameplay concept, art, soundtrack -- everything fits together very nicely. The tiling and graphics reminded me of... Sid Meier's Civilization II (the good and old) -- which hints at my age :).
The three levels seem very fit for a proof of concept, as they force the player to adopt distinct strategies (and therefore learn about the mechanics of the game) in order to succeed. The developer must have put a lot of thought into it, as even commercial often fail at this aspect. Bear with me: how many games haven't we played in which we learn how to exploit a very small subset of techniques which we repeatedly use and beat the game without learning about its mechanics? More explicitly, Gaia tolerates a more leisurable gameplay, where we can balance harvesting and exploration, Desert forces us to think very strategically and Crater makes the player use a magus.
I don't know about other people, but I would gladly pay to play more levels of this game on my Android phone.