Write a story around the game. Like something the characters are there for, how they got there etc. Your answer to "what's fun?" may come.

I used to like games with an end fight, something special to defeat or find (if it's an object to end your game or level) I dunno something with more progression. When farmville on facebook came a long I was like "why would I keep planting crops?" lol. I know this game has a farming component but maybe have the player dig for something? How are the mining mechanics?