It reminds me of that railroad game where u have to switch around the path in different directions. You play as these tiny creatures invading people, the game takes place inside a human body..or a blood stream more specifically. You have a main invader that shoots out a small invader down a path, the object is to collect white dots and bring them back to the main invader. If u get a gold dot u get two invaders and so on.... Theres also little white blood cells that also go around the path, if u touch these ur tiny invader dies and u shoot out another one, u have to be fast because the longer u take the less stars u get... It goes from 3-1. I usually get 2 stars, 3 stars Is really hard on The later levels. Besides switching paths u can also click on ur tiny moving invader to speed him up as well as speeding up the enemy white blood cells. Its hard to explain but its really fun.. Get it while its free. I was surprised how much I liked it.