Psychologists say it's the so-called happy chemicals  that are released in your brain when you score. Those chemicals give you a rush, similar to drugs. Some people can spend hours playing Slither, racking up thousands of points. It seems the more points people score the longer they keep playing.

In Slither.io, what is the difference between playing online and playing against AI? So the difference is that you are playing a computer on a.i while online are actual human players.