The third installment of Half-Life 2, and the second episodic add-on to HL2's story, Episode 2 takes place where Episode 1 left off, and on the way manages to add in some neat new features and technical upgrades. This come bundled with the Orange Box release.
Taking place mostly in the wilderness outside of City 17 -a rare departure from HL2's main urban setting - Episode 2 shows a different kind of fight, and many new species and enemies. From antlion-infested caverns (showing the two new forms of the creature, the grub-like larva and the acid-spitting worker) to the forest and its Combine guardians (including the new Hunters, a smaller, more agile version of the Strider), Episode 2 definitely shows a new side of the series. The story is advanced as well, explaining more of the backstory seemingly left unexplained at the end of Half-Life 2 - why the G-Man rescued Alyx Vance from the Black Mesa incident in HL1, what the giant bug-like "Combine Advisors" are and what they can do, and what is to be done about the portal storm growing over the ruins of City 17. Near the end, Episode 2 also references its fellow Orange Box game, Portal, with a mention of a ship belonging to Aperture Science (Portal's own deranged research corporation) that Gordon Freeman will have to find in Episode 3.
The gameplay has several new advances. The first is the enemies mentioned earlier. The antlions take a major role, as you are forced to detour through abandoned mines containing a major hive of them. The tight quarters, claustrophic area, and disturbingly realistic antlion grubs all make an in-depth gaming experience. Above-ground, Hunters are the main new enemy. They are three-legged walkers smaller than Striders that can go inside buildings and will hunt you relentlessly. The Vortigaunts - enemies in the first game, allies in the second - make major appearances supporting Gordon and the rebels with their electric and psychic powers. Later, Gordon reunites with the resistance, and using the game's new weapon - the Gravity Gun-launched "Magnusson Device" sticky bomb - defeats the Striders attempting to damage the important facilities at White Forest Rocket Facility. As with Episode 1, there is a lot of dialogue and time spent with Alyx Vance, Gordon's sidekick. For much of the game (except early on, where she is replaced with a talkative Vortigaunt) Alyx is your only human contact.
The only complaint about this game that I have is that it is fairly short. However, for an episodic-based update, Episode 2 does a good job of introducing a lot of neat sequences, gameplay styles, and new features. As a whole, it is a fairly solid game.