Play as a ball of data trying to escape from an infected computer. The player must platform their way to the exit portal of each level while running away from the virus. However, the platforms are invisible, and the player must throw a ping ball at them to push the corruption away. The player also has a fireball to throw at the virus. The virus can be knocked back but not destroyed. I built Firewall in my own engine, called Chet Engine, which you can read about here.

Here, a player throws a fireball at the virus. The virus slows down as it gets closer, until it reaches a certain distance at which it suddenly pounces.