The Orange Box*****Developer: Valve Corp.Genre: First-person shooterRelease date: Oct. 10Rating: T-MPlatform: PC, Xbox 360, Playstation 3 (Dec. 11)

If you took five video games — one honored classic, two plot-extending sequels, one modern refinement of online teamwork and one mind-bending novelty — and you put them all in a box, what color would it be?

Game developers at Valve say orange.

The Orange Box is a compilation of games that Valve released for the PC, Playstation 3 and Xbox 360. It includes Half-Life 2 (2004), HL2: Episode One (2006) and introduces HL2: Episode Two, Team Fortress 2 and Portal.

The most innovative of the bunch is Portal, a game that invites players to solve puzzles with the help of some fantasy physics.

Players are given a device that can create two distinct ends of a “portal,” which acts like a teleporter or wormhole you can see through. The player could place one portal point on the wall and the other on the floor, then jump down the hole and fall out the wall.

It feels like jumping through a mirror into the backwards world beyond, but players must realize they are really still in the same room.

The process can be confusing, but that’s the point.

Portal presents a whole new way of perceiving spaces and approaching problems.

Portal is played from the first-person perspective and leverages the physics and art assets of the Half-Life 2 engine. It’s great fun, a great challenge and the smart humor is a big plus.

The game is unfortunately short, but you can extend the magic by imagining what you would do with portals in real life.

Another offering from The Orange Box is Team Fortress 2. It is a competitive online shooter where two teams compete for territory, or strive to capture the other’s “intelligence.”

Players choose specific roles such as soldier or engineer so they can apply the right tools and weaponry to the task at hand.

TF2 is a sequel, of course, and it has done a very good job of refining the way that diverse character roles lead to teamwork. Heavy gunners pair with medics, engineers cover the snipers and demolition men cover the retreat of speedy scouts.

The game has a very cartoony look and feel to it, and the atmosphere is tongue-in-cheek, but there seems to be an intelligent purpose to its every aspect. There are many little examples too trivial to mention, but they give the overall impression that the developers behind TF2 knew exactly what they were doing.

One small gripe is that TF2 has no obvious tutorial or instruction manual (in the PC version, at least). Players are forced to figure it out for themselves and ask teammates for tips.

Who knew that you were supposed to repair things by bludgeoning them with a wrench? Strangers on the Internet are hard enough to trust already without having them advise something as unlikely as that.

Once you figure things out, however, TF2 becomes a pretty engrossing game. It doesn’t have the innovation of Portal, but it has all the longevity that the former lacks.

The other three games in The Orange Box are all part of the Half-Lifestoryline. While the first two are old news, they are still good news.

Half-Life 2 is a first-person shooter with a heavy emphasis on physics-based puzzles and its sci-fi storyline. It is commonly ranked among the top-ten games of all time, and has sold more than 4 million copies.

Episode One extended HL2’s acclaimed gameplay with new scenarios and slightly improved graphics. Unfortunately, it’s a bit slow in getting up to speed, and many of its environments are just a new spin on old locales.

The new chapter of the story, Episode Two, corrects these issues handily. It begins with a brief recap of the events of Episode One and some impressive demonstrations of the physics engine. The playing experience is roughly equivalent to HL2 and Episode One, though there are a few improvements to the heads-up display and a few new types of enemies to contend with.

Unlike its predecessor, Episode Two gets up to speed fairly quickly. Valve seems to trust that players of Episode Two will already be acquainted with the mechanics of the last two games and wastes little time in review. For instance, the game reintroduces the weapons in twos and threes, and the player has the full collection in no time.

Because of its more original environments and improved pacing, Episode Two is a bit more enjoyable than Episode One, but they are both great extensions to a great game.

The Orange Box is smart, fun and challenging, and for five games it will only set you back $50 or $60, depending on your platform of choice. If you like solving problems with physics, teamwork or guns, you can’t go wrong.