Puzzle sounds great but: this is hard to be played only as a puzzle game. You must get to the point where you learn mechanics and macro with other behavior of the game. Anyways it was hard to struggle through the monsters by trying each times just because I did not care about buildings and powerups etc. After 3 days I realized how fool I was. The lower levels give reward each time you harvest:) 2 stars still because there was no change in the gem-field so far, it gets boring at some point.