Portal

Portal is a first-person puzzle game developed by Valve and set inside the mysterious Aperture Science research facility. Players control Chell, a silent test subject who is guided through a series of increasingly dangerous experiments by the artificial intelligence GLaDOS. The central mechanic is the Aperture Science Handheld Portal Device, which creates two connected portals on compatible surfaces. Players use them to redirect momentum, move objects and reach otherwise inaccessible areas while solving physics-based puzzles. Each test chamber introduces new hazards and mechanics, including weighted cubes, energy pellets and automated turrets. As the experiments continue, the sterile facility begins to reveal a darker side, turning the puzzle-solving structure into a larger escape story built around GLaDOS and the secrets of Aperture Science.