Great, could be improved though.(Please read).
This has, Very smooth gameplay, lots of enemys, all lvls/weapons unlocked at start (may want to change that though), and well, turrets and walking characters!
Ok, now for the ideas for improvement!
1. Have it so you choose the enemy type for the lvl (must have unlocked) and the "Difficulty" be chooseable.
2. Have more of a selection of weapons. EXAMPLE: For turrets have "Basic" to something that could suck up enemys, and shoot them out.
3. Be able to SAVE-LOAD .
4. More levels.
5. Customiseable Character/Turret.
6. "Basic" Turret has unlimeted ammo, but must be shot manualy (to keep clicking, not hold).
7. Unlockable things for, Character/Turret customization (some may have speacial abilitys), SUPER-WEAPONS, levels, and so on.
8. Be able to upgrade weapons and armor, rather than just repairing or healing.
[Example of Suggestions] : For 2. have like flame-throwers and swords.
For 3. Be able to save progress so you can exit the game without losing any progress while you, well, live REAL life, then go back, load and keep playing!
For 4. Have some more levels, such as ones under water, or something like that.
For 5. Have paint jobs for turrets, and clothes (armor) for Person.
For 7. Be able to unlock things like, treads (so the turret can move, but slowly), Jetpack (so the person can fly, or rather move MUCH faster), as for SUPER-WEAPONS, how about a lazer that never needs to reload, shoots fast, but makes the user move slowly (cuz it is very VERY heavy.).
For 8. Be able to make the weapons, Stronger, Faster shooting, and, Have more ammo. Be able to upgrade armor to where it is harder to kill you, your DEFENCEIVE target, or if turret, your mini-turrets.
So yeah, lots to think of adding or upgradeing.
Please take this review into consideration, and remember only do it if YOU (and if any one is helping you) want to do it.
^-^