A chain reaction game with many features and upgrades. Basically what you are going to have to do at the start of each level is drag a virus onto a grouping of humans that are running aimlessly throughout the level. Once you do this they will be changed into zombies that will begin to chase down the other humans to infect them. You need to try to infect as many of the humans in the level as possible in less than one minute. You can drop grandes and other items into the level to get rid of zombie killers and special agents.