It just seems so simple. I know it is a flash game, but with only 4 levels with no difference between them except the amount of enemies that come, it seems so incomplete. I think this game should have had some form of upgrades, such as buying new buildings and upgrading your ground troops. Should not be one of the top games of the month.
Not sure if this is possible now, but in the future if you make a game in medieval times again, don't use that font, "b" looks like "v" and it makes the game look kinda sloppy, love the game tho, awesome. You guys should consider an iPhone version, it would work really well (more with infector style, but still)