Paper.io 2 is the territory game: you're a coloured square with a small patch of ground, and you claim more by leaving your patch, drawing a loop, and returning. Everything inside the loop becomes yours. The catch is that your trail is vulnerable — anyone who crosses it eliminates you — and so is everyone else's. Rounds are quick, the percentage of the map you own is your score, and the top of the leaderboard changes every minute.
Voodoo released the sequel in 2018 with smooth, free-form movement instead of the original's grid, and it is the version people mean. It is one of the most-searched 'unblocked' games of all, because it loads in two seconds and can be closed without losing anything.
The browser version plays against computer-controlled opponents that behave like players, which is why rounds start instantly and keep running if your connection drops.
Owning 20% of the map is solid, 50% is very good, and 100% — the whole map — is the achievement everyone chases and few get.
Yes. It is one of the lightest games on the site, runs in the browser with nothing to install, and closes instantly.