Portal 2, Valve’s follow-up to the groundbreaking, first-person puzzle game Portal, has been out since April 19 and has received a boatload of near perfect reviews and numerous accolades. Across all platforms, 3 million copies were sold through June, and that number will rise, especially if the title wins Game of the Year at the end of 2011, which is highly likely. Though it was an incredible challenge for Valve to produce a sequel on par with a game that changed what games could be, Portal 2 is truly an innovative masterpiece of creative storytelling that appeals to a broad audience and does justice to the original.

Innovative. Unique. Humorous. Immersive. Engaging. Those words were peppered throughout reviews of the original Portal when it arrived four years ago. Conceived by students from the DigiPen Institute of Technology as a project and then evolved after Valve hired them all, Portal was built around a simple mechanic: the portal gun, which allows the player to create two portals on surfaces and pass from one to the other. Because it was not intended as a stand-alone title, it was initially bundled as part of the infamous Orange Box that included Half-Life 2 and Team Fortress 2, both critically acclaimed games in their own right. Since then, Portal has gone on to sell at least 4 million copies, and that doesn’t include the number of copies sold or periodically given away on Valve’s Steam service.

What made the original Portal so groundbreaking is it’s a great story. Now, the portal gun is definitely an innovative game tool, as it challenges you to rethink your understanding of three-dimensional space and to not abandon what you learned in high-school physics, but recall it to solve each puzzle. But Portal is a game about Chell, the female test subject you embody, interacting with an inanimate companion cube and GLaDOS, your guide who eventually becomes your nemesis. There are no enemies to kill, characters to build, strategy to create, resources to manage, or players to dominate. It’s just you maneuvering your way through a series of test chambers and the Aperture Science facility for an ultimate showdown. If it’s been a while since you experienced the fun at the end of Portal or if you haven’t played and don’t mind the spoilers, check out the following walkthrough of the final fight:

Because of its rich story, the experience of Portal transcended the game as the ending song, Still Alive, appeared in many YouTube videos and was released on iTunes. Additionally, the phrase “The cake is a lie” that appears scrawled on walls became an Internet meme. Many players even reported a deep connection that they built for the companion cube. To develop a sequel to the game, Valve would have to not only capture what made Portal special, but surpass it as it would be a full title release.

Consistent with the innovation that surrounds Valve and the Portal franchise, the rollercoaster story of the making of Portal 2 is presented in an incredibly slick iPad app called The Final Hours of Portal 2, as reported by Geoff Keighley who had exclusive access to Valve during the development process and release of the game. Furthermore, Valve’s commitment to creating atmosphere in the Aperture Science facility is not only seen in the game’s visuals, but also its music. The testament to the musical achievement is the release of the game’s soundtrack broken into two volumes for free from the game’s website.

One of the best elements about the original Portal is the personality of GLaDOS, captured by Valve’s incredible writing team and conveyed through Ellen McLain’s voice, which she reprised for Portal 2. Taking a cue from the companion cube connection players experienced, Portal 2 features another sidekick, Wheatley, who is a personality core that is voiced by Stephen Merchant of Extras and the original British version of The Office fame. Finally, Valve opted to flesh out the backstory of Aperture Science in an immersive way, and its story is told through prerecorded messages voiced by J.K. Simmons, famous for his long run in the Law & Order franchise. Because of the stellar performances of all of these actors, the game’s storyline remains fresh and engaging from beginning to end.

Portal 2 also delivers a number of innovations that expand the dynamics of game play. The introduction of new light-based walkways and ways of redirecting lasers helped to add complexity to puzzle solutions, but by far the coolest elements are paint-like gels, which were introduced by another group of DigiPen students. The three gels have unique properties of repulsion, propulsion, and conversion (meaning it allows you to create portals on the gel). Portal players clamored in forums for some way to be able to play with others, and so Valve created an equally impressive co-op mode. Finally, Valve also released a map editor, allowing hardcore players the ability to mod to their hearts desire.

So now that Valve has succeeded in creating another gaming phenomenon, what does the future hold? It is clear that Portal 3 will be seriously considered, but more importantly, Portal wasn’t just an anomaly. Game companies in general will be studying Valve’s long success with storytelling in many of their games, but especially in the Portal franchise. These games are the realization of what was promised in the earliest of story-based gaming: text adventures. Graphically-devoid games like Infocom’s Zork were engaging and challenging and relied on elements borrowed more from literature than from Pac-Man to accomplish deep experiences that still reside with those who enjoyed them long ago. Portal and Portal 2 are the leaders in the next generation of those games, and here’s hoping that the broader game industry can deliver the future of games that Valve is marching toward.

For all the first-person shooters that are out there and massive battle games, Valve has made stories the core of the game. Though this isn’t anything new, the fact that Portal 2 is such a big moneymaker sends a message to the industry: story is king.

Check out the spoiler-free trailer below:

[Media: YouTube]

[Sources: Fast Company, Joystiq, Know Your Meme, Portal 2]