The crowd of zombies is walking around the place. Some of them are holding explosions in their hands, but your mission is to blow up everything you see. Set the bomb and make sure the brain will be destroyed.
Do you think zombies will spare your life if they see you on the street? No chance they would do that! So you should remember, they are not humans anymore, but a flesh with no conscious. Set the bomb and destroy everything around with a chain reaction. Make sure no zombie will get closer to the brain. Purchase the upgrades and press buttons to summon special abilities.