Play against other people online! Can you become the longest player?
If your head touches another player, you will explode and then it's game over. But if others run into YOU, then THEY will explode, and you can eat their remains!
In slither.io, you have a chance to win even if you're tiny. You can swerve in front of a much larger player to defeat them, no matter how big you are!
When a worm is defeated, the rest of the worms will get to eat it to become bigger. That's why a good strategy is trying to follow other bigger worms while waiting for someone else to defeat them, so that you can eat it and get bigger. Just like a vulture!
slither.io is a game that's got a very fun concept, with some technical issues. The game is basically silent though, as it doesn't have a soundtrack. And system controls aren't nearly as good as they could be.