A good game but has many problems.
The main problem is that you get little upgrading currency per level and the difficulty curve is too steep. There are many upgrades which are completely useless. If you want to make this game more enjoyable then lower the difficulty setting and add more gem so that people may find it longer and the upgrades more lasting. And in the later part of the game (like level 7ish which isn't even that far in) too many different types of monsters to attack and it gets very confusing. Some English errors as well.
Other than those this is a awesome game!