I just started but I have to say that I already LOVE this game. I'm really into games like this (eg TABS and the like), and this is definitely up my alley. I don't really have anything to say about the gameplay other that it's really enjoyable for me and that I'm going to play it again. The only suggestions I have would be to allow the player to put the game on fullscreen, since the UI is kind of small without it, and to show what the rewards do. Other than that, stellar job! If you have the time, I hope you can also play my game!
EDIT : I managed to get to 30 levels(?) but i accidentally clicked a link so now I'm back to 1