Diep.io is another classic game, this time with players controlling tanks, destroying obstacles and enemy tanks to gather points and level up their own machines. A reasonably involved upgrade system lets you outfit your tank to your liking, allowing you to build bullet-hell monstrosities, agile attackers, or powerful snipers.
Varied game modes, from free-for-alls to team battles and more give Diep.io some good replay value and reasonable depth, while still being a pretty accessible browser game.
How to play
Use the WASD keys to move your tank and your mouse to aim and shoot.
Diep.io was created by the same developer as Agar.io.