Sequals

Since the release of Half-Life 2, Valve has released an additional level and two additional expansion sequels. The level, Lost Coast, takes place between the chapters Highway 17 and Sandtraps and is primarily a showcase for high dynamic range imaging (HDR) technology.

The Lost Coast

The sequels Half-Life 2: Episode One and Half-Life 2: Episode Two take place shortly after the events of Half-Life 2, with the player once again taking on the role of Gordon Freeman and with Alyx Vance playing a more prominent role and expanding the mysteries surrounding the G-Man and the Vortigaunts. Additionally, one further episode is set to be released in the future, dubbed Episode Three; being the last expansion, "in a trilogy".

Episode 1

 

Episode 2

 

The E3 Beta Leak

Half-Life 2 was merely a rumor until a strong impression at E3 in May 2003 launched it into high levels of hype where it won several awards. The pushing back of HL2’s release date came in the wake of the cracking of Valve's internal network through a null session connection to Tangis which was hosted in Valve's network and a subsequent upload of an ASP shell, resulting in the leak of the game's source code and many other files including maps, models and a playable early version of Half-Life Source and Counter-Strike Source in early September 2003.

 

In June 2004, Valve Software announced in a press release that the FBI had arrested several people suspected of involvement in the source code leak 

Release the hydra-kraken! 

Reception

Half-Life 2’s public reception was amazingly positive in a lot of reviews, and it had over 6.5 million sales as of 2008. But this does not include Steam purchases, these transactions are putting the estimate at 9 million sales of Half Life 2 alone.

Metacritic ranked Half Life 2 a astonishing 96 out of 100, it is the highest game ever rated for PC on the network.

Half-Life 2 earned more then 39 Game of the Year awards, including Overall Game of the Year at IGN, GameSpot’s Reader’s Choice — PC Game of the Year Award and Game of the Year from The Academy of Interactive Arts & Sciences.

Guinness World Records awarded Half-Life 2 the world record for "Highest Rated Shooter by PC Gamer Magazine" in 2008.

Source Engine

The backbone of Half Life 2 and the episodes lie within the custom-made engine, built by Valve.
This engine, debuted June 2004, was written in C++ and incorporates everything from Platform Microsoft Windows, Mac OS X, Xbox and Xbox 360 to PlayStation 3.

SDK:
On June 28, 2005, Valve opened the Valve Developer Community Wiki.
The Source SDK is a software development kit compiled by Valve Software that is used to create maps or mods for the Source engine, with the exception of Left 4 Dead, Left 4 Dead 2, and Alien Swarm. These games are packaged with their own SDK.

The Source SDK currently has three engine versions. Choice between the 2006 version of the Source Engine, which is only used by Half-Life: Source, Half-Life DM: Source, and various mods built on old Source 2004 code.

Valve Hammer Editor:
The VHE is a  program included in the Source SDK, all versions, that allows users to create maps for the games of the Source Engine, Team Fortress 2, Counter-Strike: Source, and Portal are some examples.

Don't forget to check out my Portal Blog 

Check out the new addition.

World of Portal

My new blog about Portal and everything Portal!
It speaks for itself of course that nothing changes here and I will continue to make posts about our beloved Half Life 2 and everything it has to offer!

The infamous GLADOS

http://worldofportal.blogspot.com

The Citadel

The City 17 Citadel is the most important Citadel for the Combine, this is the base of their operations.
The Citadel was the headquarters from which the Combine govern the Earth.
Its associated portal is the primary means of communication with offworld Combine forces. The super portal is probably how the Citadel came to Earth.

It was located in City 17, and resembled a massive skyscraper, rising several kilometers into the sky from ground level, and extending some distance underground as well.
Before reaching the very top of the citadel, Freeman passes through many open areas of the citadel where enormous segments of the citadel exterior wall open and close to allow Dropships and gunships to quickly exit and enter the citadel's interior.

In the first few chapters of Half-Life 2: Episode One, the player is given a firsthand look at much of the lower levels of the Citadel.
Whilst mostly looking very much the same as the rest of the Citadel, no war factories or synth manufacturing plants are located in this area of the structure.

Style - City 17

"Welcome. Welcome to City 17. You have chosen, or been chosen, to relocate to one of our finest remaining urban centers. I thought so much of City 17 that I elected to establish my administration here, in the Citadel so thoughtfully provided by our benefactors. I have been proud to call City 17 my home. And so, whether you are here to stay, or passing through on your way to parts unknown - welcome to City 17. It's safer here. "
 ―Dr. Wallace Breen 

 Dr. Wallace Breen

Prior to the Seven Hour War, City 17 was a grand city.
Taken over by the Combine, before the story of Half Life 2, it became their main headquarters on Earth.
City 17 visually resembles a Eastern Europe harbor city featuring mostly that style of architecture-ism.
It features  styles dating from pre-World War II neoclassicism, post-war classical designs, Soviet modernism, and a mix of contemporary post-Sov design and modern EE design.

City 17 with the Citadel in the center.

The core of the city consisted predominately of wall-to-wall buildings, with blocks of clustered low-rises made out of a variety of old and new buildings.
 In addition to highways and city streets, City 17 included underground road tunnels that traveled beneath the city.

The ever-deadly Razor Train