Few companies tease its customers as well as Valve. 1998's Half-Life ended on an intriguing note, with series hero Gordon Freeman basically being "recruited" by the mysterious G-Man to work for him as a dimension-hopping commando. But fans were really caught off guard by the ending of 2004's Half-Life 2, as Gordon and ally Alyx Vance were caught in a massive explosion. Rather than have us wait years and years for the outcome of that cliff-hanger, Valve has taken the series into episodic territory to get us answers more quickly. Half-Life 2: Episode One is the first in a new trilogy of episodes that are scheduled to be released over the course of the next year. (You don't need to own Half-Life 2 to play Episode One, as it's a stand-alone product, though it would definitely help if you did.) And Episode One is a memorable romp through the Half-Life universe, with gameplay that's even more satisfying than that of Half-Life 2. The only downside is that, due to its episodic nature, it's over far too soon.

Gordon Freeman is back in action, with Alyx by his side, in Episode One, the first of a trio of episodes that continue the Half-Life story.

Unfortunately, Valve's storytelling remains about as cryptic as ever. The episode starts off on a wrong note, as there's an incredible cop-out to explain how Gordon and Alyx survive the explosion and how the G-Man gets knocked out of the picture, but it gets a lot better after that. Rest assured, answers are finally given, but keep in mind that new questions are raised, as well. Episode One is about the escape from City 17. Though the quisling Dr. Breen was defeated in Half-Life 2, the Combine remain on Earth, cut off from their alien dimension. Now, with the Citadel reactor on overload, it's a battle to escape the ruins of the gutted Citadel and the city itself. Of course, that's easier said than done, and you'll once again be plunged along a tightly controlled and highly scripted ride filled with a fair share of ups and downs.

Half-Life has always been a mix of combat and puzzle-solving, but the formula feels honed to a razor's edge in Episode One, as Valve seems to have designed content that's geared toward Half-Life veterans. The puzzles and battles seem even more complex and challenging. In fact, the best encounters in the game require a mix of puzzle-solving and combat as you desperately fight to stay alive long enough to figure out what you need to do next.

There's a wonderful new team dynamic at work in Episode One, thanks to the fact that Alyx battles alongside you throughout most of the episode. After playing on your own throughout Half-Life and Half-Life 2, it's refreshing to have a companion by your side, and Valve takes advantage of this by throwing you into situations where you must rely on teamwork to survive. Alyx is a capable assistant (perhaps almost too capable, since it's pretty tough to kill her off, and she seemingly has unlimited ammo), and she's often the difference between victory and defeat in many encounters, as she'll cover your back while you're busy trying to sort out the puzzle.

Alyx introduces a new team dynamic for Half-Life, such as when you have to illuminate her targets for her in the dark.

Spending so much time with Alyx has other upsides, as well. The flirtation between Alyx and Gordon continues even further, and while it's a bit strange that it's such a one-sided relationship (thanks to Gordon, again, never uttering a single word), you still get a feeling of warmth and affection. There's lots of humor, as well, as Episode One features some sharp and witty dialogue uttered by Alyx and other familiar faces. Barney and Alyx's robotic Dog are back, as well as Eli Vance (Alyx's father) and the ever-hilarious Dr. Kleiner. Valve's impressive facial animation is still incredible, and you really get the sense that you're interacting with believable characters in the game. Of course, it also helps that the voice acting remains top-notch. Robert Guillaume, Michelle Forbes, Merle Dandridge (Alyx), and the original voice cast remain the same.

This sense of familiarity has its downsides, as well. For instance, though extremely well done, the environments of the Citadel and City 17 were already explored in Half-Life 2, so you may find yourself encountering moments of deja vu as you battle through the episode. Your arsenal of weapons also remains unchanged. The versatile gravity gun gets heavy use through the episode, and it's invaluable to solving the many environmental puzzles in the game, but other than that, you're packing the same assortment of pistols, rifles, and grenades as before. It's also worth noting that there are no vehicle sequences in Episode One. That's not exactly a bad thing, though, as the vehicle sequences in Half-Life 2 felt fairly linear and dragged on for too long.

In terms of opponents, you do get glimpses of challenging new foes that are coming up in future episodes, but for the most part, the enemies remain the same from Half-Life 2, including the head crabs, zombies, Combine soldiers, striders, and so on. The Combine troops do seem to have some new abilities, such as the ability to rappel down buildings right in front of you. They're also a bit smarter, as they seemed to utilize cover better than they did in Half-Life 2, but you don't really get the sense of squad coordination that was seen in the original Half-Life. The only memorable new opponent is the zombine, a Combine zombie, and these guys quickly become your first target when they appear on the scene, thanks to the fact that their favored tactic is to charge you with a live grenade in hand.

Battles can get crazy, but with Alyx covering your back, there's nothing that you can't do.

Visually, Episode One introduces a lot of subtle improvements and enhancements in the Source engine, keeping it in line with video-card developments over the past couple of years. The new high-dynamic range lighting technology (seen only if your video card supports it) makes a big difference, as the outdoor scenes look a lot better, while indoor scenes feature impressive shadowing and atmosphere at times. Some of the textures in the game have been increased considerably, notably on Alyx and the other main characters, and the game looks incredibly sharp.

When you get down to it, the only major complaint about Episode One is that it's over so quickly. There are only four to six hours of gameplay, and veteran first-person shooter fans will definitely find themselves at the lower end of that range. Episode One does ship with the two existing Half-Life 2 multiplayer modes, but if you own Half-Life 2 already, you already have those. Finally, the game does include a developer commentary system of sorts, similar to the one used in the PC version of The Chronicles of Riddick, and that does provide some interesting insight into the development of the game (though the rehearsed nature of the developer dialogue makes it sound more like a lecture than a proper commentary track). But apart from that one unique feature, the only thing truly new in Episode One is the single-player story. Before you know it, you've escaped from City 17, the credits are rolling, and you're left wanting more. So in a way, Valve has teased us once again, though the bright side is that we don't have to wait long for the next set of answers to be found in Episode Two, which is due out around the end of the year.