One of the three titles in Valve's "Orange Box", Portal is an intriguing new puzzle game that mixes a mastery of physics only possible with today's technology with a bizarre, biting sense of humor. The game heralds what looks like a new era of innovation in gaming.
The story is, at first, unclear; the player awakes in a sterile white room, with various rounded pieces of furniture (all white). A vaguely malicious female computer voice begins offering instructions, and jolts alarmingly in the middle of its message. The player proceeds through the various tests, getting deeper and deeper into the mess that the facility holds - things like empty observation rooms, broken walls that lead to back alleys, and occasional glitches in your computerized overseer show that not everything is as it seems.
The main mechanic of the game itself is, of course, the portal - generated by the Aperture Science Portal Device. There are two kinds of portal that can be generated by the portal gun - blue and orange. Each portal serves as an entrance to the other - go through the blue portal and you come out the orange side, and vice versa. After the initial portals are placed, it oftentimes becomes necessary to remember which ones are where, as the player may need to change only where one end is located. The portal gun hits wherever it is shot, essentially (thus the "gun" moniker) and so a line of sight is required to create a portal. Also of note is the use of momentum in the game - essentially, if you build up speed going into the portal (ie you jump into a portal from high up) you leave the portal with the same amount of speed. This is utilized in many of the jumping problems, and oftentimes one is required to make a "loop" between portals in order to build up speed.
Next to the unique gameplay, the game's bizarre and malicious humor is its strongest point. From the clearly insane computer that monitors your every action and dispenses bits of information like "This next test is impossible. Make no attempt to solve it." and "Unbelievable. You, (subject name here) must be the pride of (subject hometown here)." to the turrets that call softly "Are you still there?" after you evade their laser sight and tell you reassuringly "I don't hate you." as you deactivate them, every bit of this game's dialogue is golden. Hazards and obstacles are labeled with "workplace safety"-style stick-figure panels at the beginning of levels, marking such possible fates as "incinerated by energy orb", "shot by turrets", and "drowned". Though cake is promised frequently by the overseeing computer, the panel for it always remains inactive; the promise of cake becomes a bitter recurring theme as the player finds the testimony of former test subjects who declare, in scrawled letters, that "the cake is a lie".
This game is as solid a package as one could hope for. It possesses a unique, masterfully executed gameplay mechanic and a dialogue set best described by this quote from writer Eric Wolpaw: "at the beginning of the Portal development process, we sat down as a group to decide what philosopher or school of philosophy our game would be based on. That was followed by about fifteen minutes of silence and then someone mentioned that a lot of people like cake." In almost every category, it is incredible.
~ Portal Walkthrough