Agar io game is a new and one of the best games in 2015. The concept is to eat other cells in the game so that your cell can become larger. The problem is when you are larger you are slower so you dont have as much advantage as you think. One of the best thing in this game is that is totaly multiplayer connected, you will play against other players so the fillings when you are the biggest cell on the server is just great - dont think that is easy to become the largest :)
Agar io game is very time consuming so do not star playing if you dont have spare time - you have been warned :D Agario game has excellent graphics and is really fun to play. Start playing and have some fun!