Portal is one of those innovative, ground-breaking games that's been so popular that even infrequent and casual gamers have played it. The praise is well deserved. Fundamentally, Portal is a classic first person, puzzle level game in which you must get through various game levels. What radically differentiates the experience, though, is that in Portal you are equipped with a portal gun that you use to make portals in the walls, floors, and ceilings.
This enhancement forces you to reconsider the typical spatial awareness in game levels and think in portals. The implications are fun and far-reaching. For example, you sometimes need to create two portals on opposite sides of a room to bypass a chasm. Or you may have to create a portal on the floor a few levels down and an exit portal high up on a wall so you can jump into the portal below and have your momentum take you from the portal above to a high, previously inaccessible ledge on the other side of the room.
You are led through the game by a computer guide that adds an inventive twist that makes an already good game great. Finally, the ending credits feature a catchy song that is worth sitting through.