Slither.io, it is free for all battlefield type games and is certainly one of the most popular io games on the market right now; here agar.io you play as a snake in a similar world and try to gain size while removing other snakes controlled by the player. There are tons of small food spheres to gather around the map, which will slowly but certainly increase your snake size, and you can also gain size faster by consuming an enemy snake. The goal of this game is ultimately survival, but some of the more competitive snakes also aim to become the biggest and worst main trucker there by reaching the top spot on the leaderboard.
No matter how big you are in Slither, you can always be eaten or eaten by a bigger / smaller opponent, it's all about how it can turn you into a dangerous encounter or snake food. To defeat another player, you must make your snake's head collide with your body, and avoid hitting another; It's important to remember that when a snake dies, it will turn into some food sphere that fits its size and can be eaten by anyone, so eat quickly and make sure no one else benefits from your hard work!