Slither.io is a new game/app which is taking off in a really massive way. Loosely based off the Agar.io series, it is a game where you play against hundreds of other players across the world and in real time.
The aim of the game is simple; grow as long as possible by eating the glowing food which is left on the map, but if you crash into another snake, you lose. The longer you get, the wider you get thus you lose more flexibility overtime but you also have room to outmaneuver your opponents. Think of it like the classic game of Snake on Nokia phones.
Since being created in 2016, the game has grown and grown and is now one of the most visited websites in the world. What makes these games so successful are how easy they are to play for children and adults alike. You just have to avoid other snakes, theres no levels, no maths, no skill needed to play. Anyone can play and it can be super fun.