Diep.io is a game about cannons shooting other cannons. Created by Matheus Valadares and released in 2016, it became a quick hit, and is still a popular .io game.
Players play as tanks that try to shoot at each other, as well as randomly generating polygons. This allows players to gain experience, eventually leveling up, allowing them to purchase upgrades. Players can also choose a tank build upgrade at levels 15, 30, and 45.