One star only because...
I’m leaving a one star in hope that developer will see it and fix this flaw; I got stuck in level 7, because the secondary objective is to collect 400 mana. In the middle of gathering 400 mana, I went back to the castle to do an upgrade on the spell, which reduced my mana pool and now I can never reach 400 even though I cleared everything out from the map. I revisited all the older level and there just isn’t enough mana treasure around to ever reach it. Now I’m stuck and it doesn’t make me want to start over because of this.