A lot of effort put in... but...
Unfortunately a rather terrible game. The production values are high. You have fantastic art for the in-game stuff as well as sound, decent music and an okay plot that's one of the only contemporary plots I've seen. You have realistic environment and sounds, which is great. However, even production has some severe issues.
The English is terrible and the actors are a bit odd. They don't really come off as American at all and it makes the setting somewhat confusing as well as the plot interactions rather ridiculous. Actors, you might not be able to do much about, but you should've definitely had someone versed in English go over the script and at least clean it up some.
Music should have been used more during gameplay and cutscenes rather than just set pieces, and lack of music added to the general boredom I found with the later levels.
Moving onto mechanics... the interface is confusing, the HUD gets in the way of the right side of the map, and your options are extremely limited. Four types of units, repair, sell... and that's about it. When you consider games like Zombie Horde which allows free movement, or similar tower defense games with dozens of weapons... it's really kinda stale. Add more weapons. Add barriers, which are easy and basic, maybe command attacks like mortar strikes and helicopter runs.
As for everyone's complaints about difficulty? I found the first levels "just right." The map was intelligently designed to allow some difficult, but manageable killing and I got through the first nine or so without having to restart. However, when you brought in all the armored vehicles, you have this issue of units dying so fast that you have to either build new units, or heal old ones. There's no in between because money is sucked up so fast. And if a single unit goes past the cluster of guns you have to build, then suddenly you have to scrounge money to place a turret just next to the level exit.
Yes, I agree with everyone else. ONE HIT LOSE DOES NOT WORK!
The graphics and poor zoom level also make it hard to tell the units apart, making me unsure if I'm repairing an M60, or a vulcan... which becomes fatal when I'm frantically trying to repair a bunch of units getting pummeled by armored vehicles to preserve my "score." Also, being unable to repair if low on money was dumb. You should be able to repair partially. I think a system like click on a unit to repair $50 worth of damage per click would allow you to both save money and keep your units alive for longer.
So I guess that's that. A lot of effort is in the game, so I'm sorry to see it came out as disliked as it was. However, you have all your materials on hand, and you can definitely create a fantastic game with the resources on hand.