The curious case of the .io genre began in 2015 with a single game going by the name of Agar.io.
So named for its cell-like theme ('Agar') and the top-level domain name it existed under in its initial web browser guise ('.io'), Agar.io provided a blissfully simple, massively multiplayer online experience. The idea here was to gobble up smaller cells to make your own avatar bigger, with some of those smaller cells taking the form of your fellow players.
In the wake of its huge success (aided no end by swift Android and iOS ports), a string of games inspired by Agar.io popped up. And thus the .io genre was born.
We now have ourselves a thriving little .io sub-genre, filled with games that have begun to stretch the form in new directions.
With that in mind we thought now would be a good time to round up some of the best and most popular .io games on the Google Play Store. Is you favourite missing from our list? Let us know in the comments below.
This 3D arena battler sees you chucking axes at your foes as a Viking warrior. Axe.io is far more fleshed out than your average .io game, with multiple modes and a pronounced progression system. It's the .io genre all grown up.
Here's the game that started the whole .io craze off in the first place. Agar.io is all about growing your cell as much as possible, gobbling up the smaller play cells as you go. It looks pretty ropey these days, but still plays great.
It's not labelled as an .io game, but Crash of Cars certainly follows the 'every person for themselves' .io template. This time, though, the carnage is automotive and the graphics are uncommonly slick.
Probably the cutest .io game on the market, Mope.io is also a little bit different. You're still gobbling and growing, but both of those activities are handled with a little more nuance and variety than normal.
Paper.io 2 isn't particularly original (heck, it's even a sequel), but it is one of the brightest and slickest .io games out there. It's one of those where you must cordon off areas if you want to expand, adding a dose of risk and reward.
It's Snake, but multiplayer. Or, if you want to be cooler, a casual version of the Tron bike-maze game. Guide your creature around an arena, attempting to trick your enemies into crashing into your extended tail.
Hole.io pinched the 'control a hole' premise from Donut County ahead of that game's launch, which was a bit naughty. But it then applied that to the massively multiplayer .io genre, so it's not a total clone. And it's undoubtedly fun.