Nice concept, but there are a few problems.
First of all, the font is very annoying. As cute as it might be, that type of font is too decorative to use for anything other than a title. It's hard to read and not user-friendly. Secondly, the game gets very boring very quickly. While idle games can be successful, it sucks the fun out of it in this one. The fight happens too fast to see and that makes the battles boring. Upgrading is too basic to be any fun either. And the number of monster types are limited, which, combined with the basic upgrades, makes leveling up much less fun. Overall, it's not the worst game, but it has a long way to go.