I thought agor.io would be hot JTK pics ._. Turns out it was the boring thing again, didn't even scare me >.> I'm addicted to that game now, I rage everyday ;-;
Agar.io is the basic principle that big things eat small things. Your cell follows your mouse and the green non moving things are a shield to hide and the red ones will kill you if you go inside but they give out tiny cells. There are 3 gamemodes (I think they added one, correct me if I'm wrong) which is ffa (free for all) ,teams, and the last one that I don't know since I've been trying to avoid going on agar.io again.
The green ones are viruses/viri and if this is you 'you>green thing' then you explode when you hit them. The red ones are the mother cells, the third mode is experimental