Paper.io is a popular online unblocked multiplayer game developed by Voodoo, where players compete against each other to expand their territory by drawing lines and capturing as much space as possible. The game is set in a square grid, where players control a small cube character that can move around by swiping in different directions using the mouse or keyboard. The goal is to create closed shapes by drawing lines, which will then fill in the space and become part of the player's territory. Other players can cross your lines and destroy your territory, so you need to be careful and strategic in your movements. You can also attack other players' territories by crossing their lines and destroying their shapes. The game features various power-ups that can help players gain an advantage, such as increased speed or invincibility. There are also different game modes, including classic mode, where players compete to get the highest score, and Battle Royale mode, where players battle it out until only one player is left standing. Overall, Paper.io is a fun and addictive game that requires quick thinking, strategic planning, and precise movements to succeed.