tl;dr: Overhaul AI, beef up walls, add music and sounds.
Like everyone is saying, this is a game with great potential. My main concerns are:
1. Random AI - It would be cooler if they didn't wander around like assholes. Or if you could assign them spots to guard, maybe turn the walls that extend your land into guard towers? Also, maybe throwing gold at a villager with a job will make him work faster, or even upgrade him?
2. Trolls trolling so hard - Like others have said, those walls are too damn thin breh. It wouldn't seem so bad, but between my walls breaking every wave or two and the AI being a jackoff, it's rustling my jimmies pretty thoroughly. I've also had a troll jump over my wall and kill a villager who dropped two coins, but the troll accidentally missed the coin from the height of the jump and just kept going to rape my scythes instead of doubling back for the gold.
3, Needs some jams - I think you should have music for both day and night, and you should make the trolls make some kind of noise when they walk/show up.
4. Final notes - I would like to see better aiming from my archers (upgrades?) and I would like to see unpaid citizens (I'm calling them brownies) run after gold when I drop it. It's annoying to have to dunk the gold on the top of their head for them to get the point. And possibly assigning jobs to farmers blah blah blah, look, you've got a standup game here. I think everyone agrees that the AI needs an overhaul, but other than that, the game is almost perfect.
I love and miss these kinds of graphics in games, and the simplicity in the controls is refreshing. Please make a sequel, I know it will be better.