In this game you play a small robot inside of a human body. Move toward the brain in the brain stem, destroying malignant tumor cells until you finally get to the brain where the main tumor is. The brain tumor shoots malignant cells at the player. You must destroy it.
It helps to hold the mouse click button down while moving. The laser will eventually run out, when it does release and fire again.
It is possible to kill multiple enemy cells with just one blast if you hold down long enough.