The human kingdom has been invaded by an army of monsters that are attacking major cities. You in the game Mad Defense will help the mad scientist to protect the city from the invasion of monsters. In front of you on the screen you will see a defensive tower on which your character will stand armed with a certain weapon. Various monsters will move towards the walls of the city. You will have to catch them in the scope and open fire. By shooting accurately, you will destroy opponents and get points for it. With these points, you can purchase new types of weapons and ammunition in the game store.