It is a fun game where you are like a human cell and can eat other cells for points, but you need to be bigger than the cell you want to eat or they will eat you. The more you eat the bigger you get. It has hundreds of people playing it and is a lot of fun. The game is free and you can play it here too
Just use your mouse to move the cell around. It is a really simple game, but lots of fun too. Just play as a guest.