Your objective is to kill all 5 bosses without dying. When you die you'll be taken to a store screen where you can use money you earn from killing zombies on a number of upgrades and weapons. You get as many attempts as you need, and the game will tell you how well you did based on how many times you died before finishing the final boss.
There are number of power ups unlocked by getting a large combo (by killing zombies quickly without losing pace). These include 2x gold, 2x power, 2x speed, and bonus gold.
The game auto saves so you can go back later and keep all your guns, upgrades and armor.
Retro inspired pixel art graphics were used to give the game a slick and unique feel. The graphics are entirely original and includes a huge amount of content in terms of backgrounds, barricades, zombies, bosses, and a variety of armors for the main characters in addition to the games unique interface.
Use the arrows or AWSD keys to control your character. Use the mouse to aim and fire. Press P to pause and M to mute the game.