Very nice game. I made it until difficulty level 23. I died because of the slimes that split appart in multiple enemies. I had hard time to understand the build mechanics (buy, then drag n drop on the map). Same for the power ups you have to be very precise to bind them to your envoys so I got the mechanics right mid game ^^ I'll give it another try as I love tower defense games and I used to develop one for a long time! :)