Up next was a sequence featuring the new car, a beefy muscle car whose entire front bodywork has been destroyed, leaving its large V8 engine exposed. In Episode Two, Alyx rides shotgun, armed with a pistol. As in Half-Life 2, I am still not particularly proficient driving in first person shooters, and my scenic trip was punctuated by numerous crashes into rocks and trees. A Valve developer assured me that the sequence is not the first instance of the car in Episode Two, and that there is a driving proficiency curve designed into the game.

The destination is a small cluster of shacks situated upon a forested plateau. From a rocky vista, the sprawling, smoking landscape surrounding the Combine citadel is visible. That evocative vignette is a touchstone throughout much of Episode Two, serving as a visual focal point in the background of many of the game's expansive outdoor environments.

After restoring power to the outpost in order to gain access to its radio tower, several Combine Hunters show up for the most thrilling battle in the Episode Two preview build. Essentially smaller versions of the huge three-legged Striders from Half-Life 2, the nimble Hunters travel in packs, are much more tactically-oriented, and have been tasked with eliminating Gordon and Alyx. This Hunter battle--which can play out in, around, and/or on top of the few structure clustered on the plateau--is not quite in the same vein as past Half-Life battles, which tend to be fairly enclosed or directed.

Fighting Hunters is different--they will track you as you hide in buildings, burst through windows to surprise you, coordinate with one another to flank you from both sides, climb up on top of a building for a better angle if you've taken cover, and generally just be a lot more clever than most FPS enemies. I had to fight the battle a few times before I was able to take out all of my foes, and each time felt noticeably different. In fact, I found myself wanting to go back and try it again, just to test out my improved knowledge of the Hunters' battle tactics. Rather than getting better at remembering the set pattern and better attempting the "correct" shots with each attempt, I was actually becoming better at outwitting the Hunters on a strategic level.

To even the playing field slightly, Alyx comes equipped with boosted AI as well, further iterating on her already improved logic from Half-Life 2: Episode One. Alyx remains one of the focal points of Valve's development, both as a way of demonstrating new or updated Source technologies, as well as continually establishing her as one of the player's most significant connections to the world of Half-Life. "We felt it was important to continue to invest in Alyx," Speyrer explained. "The more effort we put into her, the more we get back."

Alyx is now better equipped to fight in an arena setting rather than just a forward push. She will take position herself more tactically, take cover behind objects or windows, and even take blind shots around obstacles if the situation is too dangerous for direct exposed fire. Along with her AI improvements, Alyx has received various visual tweaks.

After the Hunter battle, it was back to the car. A short drive leads to a group of resistance fighters holding out against a mine-dropping Combine helicopter. The segment provides another showcase for cinematic physics, as large parts of the cobbled-together sheet metal resistance encampment explode and rain down onto the ground during the helicopter attack. In a typically enjoyable gravity gun-centric "boss battle," the helicopter's own mines can be used against it if flung back up at the aggressor before they explode.

Helicopter down, back to the car to arrive at the rural village of White Forest, the destination of the Combine army seen earlier. When Gordon and Alyx arrive, the town is empty, creating a serene pastoral image. It isn't long before things heat up and the place is infested with Combine soldiers and Hunters. Due to the size of the opposing force, the battle is not quite as tactical as the sparser plateau fight, though it is certainly more frantic. The

Combine set up force fields blocking off choke points at either end of the town, creating a contained arena. Despite the enclosure, there is a great deal of available area in which to fight, with numerous buildings each multiple stories tall. As soldiers push forward in fairly obvious routes, coming through doors and up staircases, Hunters prove more resourceful, taking unexpected paths through a basement or from the back of a building. The amped up battle, with its greater focus on the confusion of high-paced indoor fighting, is a nice counterpoint to the previous, more wide-open and tactical, Hunter encounter.

Upon the completion of that battle, the preview ended, having demonstrated a Half-Life that is, if not necessarily a radical departure from prior games, a significantly expanded and evolved one. Team members noted that, while the emphasis on greater player choice and more open situations has led to numerous design challenges, it has also opened up many gameplay and narrative possibilities. "More choice equals more potential for bad situations," said Speyrer simply--and, of course, the Half-Life games are as much as anything else about a string of bad situations.

This makes Valve's new commentary feature, which the company plans to include in all of its games going forward, all the more enticing in Episode Two. "People loved [commentary] in Lost Coast, so we did more in Episode One, a silly number--I think 90 or something. Then they said, 'We still want more,'" laughed Speyrer. "Well, I don't know if we'll be able to have more, but we'll try and match that." The developer pointed to commentary as an example of a feature that would be much more difficult to include with a full-length game release, but that is well suited to the company's current model.

Along with the new nonlinear encounters, Episode Two features an updated auto-save system that checks whether the player is in the midst of combat before saving the game. This avoids situations of an auto-save happening at an inopportune moment, a situation that would otherwise be more likely with Episode Two's potentially very long battles.

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Valve's current completion estimate for Half-Life 2: Episode Two, which will ship for PC, PlayStation 3, and Xbox 360 along with Team Fortress 2 and Portal, is late September or early October.