Essentially a puzzle game, Portal 2 requires players progress through a series of rooms using critical-thinking, creativity, and flexibility to progress through the maze environment. To be successful, players must use items in the game, such as the portal gun, a gun-like apparatus that creates portals between various surfaces, and cunning to be successful. As players progress, additional items are introduced including propulsion gel, turret attackers, and thermal discouragement beams, so the number of elements necessary for puzzle solving increases. Players must use knowledge they have gained from previous puzzles, while remaining flexible enough to recognize opportunities to use these elements in new ways. In addition to single-player, Portal 2 also features a cooperative-campaign in which two players must coordinate their actions and resources to successfully complete more complicated puzzles. Throughout both campaign modes players continuously practice 21st century skills while enjoying the immersive environment of Portal 2. By recognizing and leveraging learning potential in Portal 2 and other video games, educators have the opportunity to teach important lessons while players just play.