Portal is an unconventional take on the First-person shooter, and is a unique, engaging, humorous experience.
You play as Chell, a human test subject of some sort at the Aperture Science Laboratory, and in the beginning you have no idea what you are doing there, very little is explained to you besides the instructions you must follow.
The visuals in this game are fairly well done, despite being a little bland in terms of color and detail in many of the stages.
All gameplay in the game is made with the portal gun, which is your only weapon throughout the entire game. It is your tool with which you problem-solve and navigate through the Aperture Science Laboratory. The environments will force you to place portals in places you never would've thought about, and you actually have to time your jumps and sometimes even your portal shots according to where you want to go. This makes for some pretty interesting gameplay through taking advantage of gravity.You often have to manipulate physical objects in order to move onto the next level. Knocking over sentry turrets just never seems to get old, provided you're not in range of their bullets.
There's very little music in the game besides the song at the end, which is possibly the best ending theme to a video game in history. Plus, with GLaDOS' hilarious dialogue, the player begins to feel a sense of companionship to her, until she threatens to kill the player. In fact, everything about Aperture Science just seems laughably absurd, and even the sentry turrets seem to have a personality of their own.
All in all, Portal is a joy to play. Sure, it's short and doesn't feel like a full-fledged single-player game, but the casualness of solving puzzles, combined with actual FPS controls, along with creatively developed characters and setting, all add up to create a powerful blend of both storytelling and gameplay.