This game is truly challenging and amazing. The graphics are very nice, the sound effects are subtle and work very well with the graphics. The upgrades are great and the gem compositions are challenging yet fun to play around with. Your hard work comes through in this game, I haven't played the prequels yet but I'm about to start.
To all those people who are crying about the fact that you have to "pay", show some respect to the artist/s who work extremely hard to make these games. Artists have to eat also...