This is an alright game but needs updates to make it a great game.
Number one, you need to have some levels give a little less or little more reward upgrade points. Depending on how well the player beats the level. If they didn't get the full point reward than they can retry the level to get the rest. Yes this might be annoying and unfair, but will make it more interesting instead of the simple 5 points no matter what. This will also include harder level=more point reward.
Different zombies should give different cash rewards. As I can see all of them give you 25$ for each kill, no matter what zombie you are killing. This is annoying to me because if they throw a hard as hell zombie in your path and you are getting the same reward as a weak normal zombie, you go what the hell? This makes the game harder this way but it can still be hard if you change up the dollar system in the game. Like with each upgrade you have to pay a little more than 250$. To me, you took the a shortcut on the money system.
Upgrades needs to be a little more interesting. Since I suggested increase reward upgrade points you can put in another upgrade that will make the game more interesting. Like snipers can have increase of range, gunners can have increase of fire rate, the bombers can have increase of cluster bombs, ect. Something that will make them stand out will be a god send.
This is an option but you can have a zombie research station. Since the plot of the game is that you are in charged of defense, you should be able to have some Intel of the different zombies you are going against. The more Intel you have, the better you are against that certain zombie.
This one is necessary, since certain zombies have range attacks and can destroy your torrents you need to have a single targeting system in the game. Like I can click on a zombie and see it's health and range, but none of my attackers will all target that single zombie. This is annoying and very costly because these range zombies are in groups of different zombies and the attacks see them as last thing to target. Yes I can increase the torrents armor but this will just pill up the range zombies into one dangerous group where all you can do is bomb them.
I like it how you have random cars in the way, shows realism in the game. But you can add an option to move certain cars in the way, to slow them down, or to make them walk in a line. Certain cars are so crashed up that you won't be able to move them or use them, while certain cars you can still move and push.
Lastly, have troopers move. I have been playing for awhile and I have yet to find a way to move your troopers. This would be useful since they have feet and I can use them to push the enemy back or to fall back.
This is just a little list of what I think will make this into a great game. If you don't use all, just use same and I will call this game a win.
