This game has a fun value through the first 4 levels. Once it hits the 5th it becomes painful and somewhat unfair. That is until the upgrade system makes sense. once you have lost and upgraded enough, along with using the same strategy as the AI enemies, it becomes fun again. My only issue was that past level 5 i could sweep through 6, 7, and 8. there are multiple times like this where the specific positioning is overly helpful to the player, making half of the higher levels easy. To improve this it would need better level balancing. finishing the 20th level with ease should not happen even with the highest upgrades. In the end only 3 levels force you to think strategically and level up units with a plan in mind. Other than that the game is rather fun.