Portal

Portal is a 2007 first-person puzzle game developed by Valve, in which a silent test subject named Chell navigates a sterile laboratory using a device that fires two linked portals across flat surfaces. It was originally released as part of The Orange Box compilation of Valve games.

The core mechanic let players create two connected openings on eligible walls, floors and ceilings, then step through one to emerge instantly from the other, using conserved momentum, physics and spatial trickery to solve a series of escalating test chambers. Its brilliant, tightly focused puzzle design was matched by the darkly comic, gradually unsettling narration of the rogue AI overseer GLaDOS, whose promise of cake became a running joke.

Portal became a phenomenon celebrated for its inventiveness, ideal length and sharp writing, coining lines and memes that entered wider pop culture. It remains widely available digitally and stands as one of the most influential and beloved puzzle games ever made.