Like the original Portal (2007), players solve puzzles by placing portals and teleporting between them. Portal 2 adds features including tractor beams, lasers, light bridges, and paint-like gels that alter player movement or allow portals to be placed on any surface. In the single-player campaign, players control Chell, who navigates the dilapidated Aperture Science Enrichment Center during its reconstruction by the supercomputer GLaDOS (Ellen McLain); new characters include robot Wheatley (Stephen Merchant) and Aperture founder Cave Johnson (J. K. Simmons). In the new cooperative mode, players solve puzzles together as robots Atlas and P-Body (both voiced by Dee Bradley Baker). Jonathan Coulton and the National produced songs for the game.