As of me writing this, I've been playing for about 2 days. I'm probably going to get another day or two of enjoyment out of it and actually be done with it by the time this post actually gets published.
And I'm ok with that. For now, it's just fun being a mouse on a giant tortoise shooting a machine gun at incoming bugs. You can upgrade things, add units, go to a new generation of tortoise for permanent bonuses and other stuff too.
But the main part of the game is being a mouse shooting a machine gun off the top of a giant tortoise. If that interests you, take a look. If it doesn't... I really don't know what else to tell you.