love it!
I really enjoy playing this game, and I hope you make a sequel with a few improvements;
1. Experience points or something of the like to provide other upgrades between levels, besides only unlocking things after beating levels. Things like the amount of land available to build on, starting money, cash per kill, max heath of your wall and the like wound be nice.
2. Difficulty options would increase re-playability.
3. Increase the difficulty on endurance mode. At a certain point i just let it sit and had over $50,000 when i came back.
4. MORE LEVELS!!!! (it is fun, and i want more!)
Great game, keep up the good work!
P.S. I love the story too, keep expanding