Really good game. Good concept and fun. Appropriate upgrade tree for each level. I'll echo the magnet upgrade comments. Also, I think the game would be better with mini-bosses every ten levels and a super boss after level 40. Who wouldn't want to send their penquins after Morla, the Ancient One or the Turtle of Enormous Girth?
I have agree with alx222000 about the grinding nature of this game. Especially when it comes to the "courier" missions for the guilds. Those are pure torture. The constant random attacks are killer. Also, it would be great if there was a way to level up the character. You just get six points at the outset and are stuck with that.
All that said, I find the game strangely compelling and addictively boring.