So this totally looks like it could be a good game but unfortunately the dev took great length to make it not be one. There are obvious bugs like you can not finish the tutorial because the UI elements overlap each other and the things that you need to click. Or enemies that can be outside the screen damaging your wall without you being able to do anything about it.
The slow progression is extremely annoying. As is the bad aim of the "heroes". If you save up to get another hero like the cannoneer, thinking that the splash damage might at least offset the bad aim, you will get even more disappointed because their aim is even worse, rendering them almost worthless.
The game forces you to constantly click on the enemies and there seems to be no way to automate around that. That clicking gets tiresome soon. Then you do not really have time to manage the updates of your heroes taking all the fun out of a potential micro-management.
Too bad, this looked like it might be fun.