There are three major bugs that need to be fixed that would make this game greater. First, monsters and upgrades are enabled with the hotkeys even if you can't see them. Sometimes, you go on the negatives in gold because some abilities trigger twice by themselves. When your gold is zero or less because of the last bug, you can't cast spells, because you don't have enough gold even if they are not supposed to cost anything. Please plus this so developper can see it. :)
This game is fun but a little something need to be debuged because the upgrades are made irrelevant. If you use the hotkeys you'll be able to upgrade spawners without paying the stars. :P
Warning, if you try to use the breeding reset on female by selling them and removing them, you could make the game crash and loose your saves. It happened to me while trying this trick.