Gets boring and anoyying fairly quick
Okay first off, you used all sprites from other games. The health bar/system from RE, and the sprites/backgrounds from Metal Slug. Upgrades were an okay thing, they didn't seem to do much however. It was fun for awhile but the fact that the mines can kill you so easily became anoyying.
I'd suggest just to make it so:
-More weapons
-Lower Zombie HP, Raise amount