Half-Life 2 is one the most anticipated games of all time but fans have had to wait as it continues in development. BBC News Online's Darren Waters met its lead director, Gabe Newell, at the E3 games show in Los Angeles.
Twelve months ago a demonstration of Half-Life 2 stunned the video gaming world at the E3 show in Los Angeles.
Huge hype surrounding the release of Half-Life 2
The sequel to one of the most important video games of all time, it featured unprecedented levels of visual realism and a unique ability to interact with the virtual world.
It was planned for release in September 2003 but the date came and went, disappointing millions of gamers.
A high-profile theft of the game's source code by hackers, brought the project more problems.
A year on and Half Life 2 is once again being demonstrated at E3, and again impressing fans.
"We certainly would have rather we had it in the shops by now," admitted Gabe Newell, the managing director at Valve Software.
"We just have more work to do and it's taking us longer to get that work done than we anticipated," he added.
The level of anticipation surrounding Half Life 2 is enormous, equal to the hype surrounding a new Star Wars film or the Lord of the Rings movie.
When the original Half Life was released in 1998, it re-wrote the rules of gaming, mixing a cinematic-style narrative with explosive action.
It also spawned a sub-industry of so-called modders, gaming enthusiasts who, with the blessing of the original creators, were able to adapt the game and take it in new directions.
Counter Strike, perhaps the world's most popular online action game, is a variant of Half Life and there are many other games based on the original.
"Our bias is always to focus on making the game as good as possible rather than just getting it out for a specific date," said Mr Newell.
"It's hard on us and hard on our fans but hopefully in the long run it is the best decision."
Half Life 2 features a character called Gordon Freeman, a scientist caught up in a world of madness.
The demonstration at this year's E3 once again showcases a visual realism seen only in animated films and not in video games.
Mr Newell said: "We want to arouse an emotional response in people. How can we make the world feel like it is part of the gameplay rather than just being a stage where the game occurs?"
The emotional response in people who have seen the demonstration is certainly strong. The game draws gasps of amazement and astonishment from the few who are ushered into a screening within the E3 show.
Mr Newell admits that there is a lot of pressure on the Valve Software team, who want to ensure the game does not disappoint any of Half Life's fans.
The original Half-Life had a lasting impact on gaming
"We want for the people who played the original and gave it all those awards to say it was a worthwhile successor that we lived up to that potential of building an immersive, interactive world and playing you inside of it, almost like a movie."
There is certainly an expectation that Half Life 2 could be the first game to truly create the experience akin to an interactive movie.
Mr Newell said the theft of code last year was hard on the team, especially when unfinished versions of the game appeared for sale online and, reportedly, in Russia.
"We are sort of perfectionists and the idea that some people could take some random pieces and slot them together and sell them on a website is hard on the team.
"It's like a movie and some people releasing an unedited cut on the internet."
Mr Newell said the firm had to change the game's network code, which dictates how the game is played online.
"We had to change the code to stop people from cheating when playing multiplayer games."
With no opportunity to play Half Life 2 at E3, the game remains high-profile, high budget and still highly under wraps.