A lot missing.
First off, I'd like to talk about what's improved. The graphics have gotton better a bit, but it still dosen't feel like a defense game. Perhaps if you would've been planted inside of the building with the enemy coming out to attack you instead of you being out to the site it would've been better.
Secondly, the accuracy is far better. On the last game, I had trouble hitting anything if I shot for more than 1 second. With this, I can still hit things up to around 2 seconds. It makes things easier on the targeting and thus makes the whole game easier. The other thing is the repair bar. Last game you coudn't repair all, but in this one you can which makes it so much easier and less time consuming.
Now the game, for what it is, has a lot missing. What these games thrive on are the upgrades. All you have are weapons and the sight for them, which I never found out if they work automatically or you're supposed to equip them. Maybe I need to go over the controls again.
Anyways, all you have are weapons. That's it. You can't buy extra men to help you, you can't buy turrets, and you certainly can't buy wall upgrades or even base upgrades. It really leaves me bored after the first few rounds. There's nothing to strive for.
Maybe, if you make a Palisade Guardian 3, you'll incorporate this. I certainly would like to go through all 35 levels with that, but how it is, I start to lose interest at around 5.
It's really lacking.