Move your mouse to move and aim him. Avoid hitting the viruses or you will loose a life. Click to attack and kill currently kill-able viruses. Kill-able viruses are indicated at the top. If you pickup pills, you would be able to fry all the viruses you touch for a limited time. Meet the level target to level up. You can upgrade at the level up page which enables you to fry selected enemies by touch. Lets defend.