It's a great base for a game, but I wouldn't call it "TD". And despite that, in this condition, it doesn't get difficult at any point. Maybe it can be improved out a bit?
Finished with a 7.0. 3/5. Not bad microgames, but the fast switching from one to another, along with the fact that you must continue the game exactly where you left it leaves you pretty short chances to extend it. Not bad, but frustrating in excess.