Nice TD!
However, there are few small things:
1) There are 3 upgrades in shop: I, II and II. Should the 3rd be III?
2) I try to send all the waves as soon as possible in lvl11, but I still can't get time bonus.
3) You can sell your health. That is only bad, since you lose money bonus after level, because you are not in full health, even if none of the ravens pass.
4) It is difficult to place towers under top row, since that status bar is on the way.
5) Since lvl 3, I have survived by placing and fully upgrading towers near the entrance.
6) No matter how money you have in the end, it is lost. I hoped to save some to use it to buy upgrades from the shop...
I'll keep playing, next lvl 12...