Good game overall but... 1. Amount of ads in here are too much. I understand the need of ad but maybe set it to be beginning before you start your campaign? Half way between levels are quite intrusive. 2. Hard to become stronger 3. Passing 30 waves in one go is too much. A check point for every 5 to 10 levels is needed. Few times I died at level 29 and need to start completely again from level 1...