Very good game
This is very good next time make like online multyplayer so u can work together at base while u get attacked by :Eazy(1side to def) Medium(2sides to def) Hard(3sides whit army/suvivor help) Bonus(whole screen wit base in the mid, u can get out of the base to take enemy weapons u also get army help)(army help=helicopter that land troops whit m4)
Also in singleplayer make sure u can place ur suvivors and base.
New weapons:
Bazooka(limit ammo, can only be droped by enemy),
Machinegun(unlimit ammo, but has to be buyed in bonus modeand only in base.