The OP here Yes, the Game is indeed free, but only with basic feature to get excited about the app. Then the user should upgrade to get access to the other cities and unlock level.

The real issue is not only the big 0 income, but the fact that after 3 week we barely pass the 100 downloads. Google advertise everywhere that there are more than 1M new android activations everyday.... Those are potential users of any game right.

What is not quite right I believe is the discovery of new app on the market. It took us 13 days to start appearing on the 20th page of the search "sudoku".