I really love the visuals of this game, the graphics are really well done. I think it's quite easy to pick up too so it gets you right into the action.
I didn't see the biggest correlation to the theme but ultimately I do just like a farming game!I think a few tweaks might improve it a lot and make it a really pleasant game to spend a good bit of time on. Sound for actions would have helped a lot, and I felt that the upgrade screen tended to interrupt me - maybe this should happen more at the end of a wave or day rather than at level up. I also wasn't sure what the tools or different plants did.