By Alfred Hermida
BBC News Online technology editor
Gamers have been able to get a taste of the technology behind the widely anticipated Half-Life 2 PC game.
The popular online game has had a major makeover
Late last week, the game's makers released its multiplayer companion, a revamped version of Counter-Strike.
The popular online game has became a showcase for the Source engine developed by Valve.
Source is the underlying software code behind the Half-Life 2's life-like environment, realistic physics and improved visuals.
The leading edge technology will power the long-awaited Half-Life 2 PC game.
The game's publisher, Vivendi, has not yet set an official date for its release but it could be in the shops in late November.
"We are still hopeful, however, to see the game on store shelves this fall," Valve spokesman Doug Lombardi told BBC News Online.
But fans who cannot wait have been able to sample some of the features promised by the Source engine as Valve has used it to power a new version of Counter-Strike.
However, the game can only be bought as part of a Half-Life 2 bundle via Valve's online delivery system called Steam. Counter-Strike: Source can be played immediately, but Half-Life 2 is locked until the game is officially released in the shops.
Counter-Strike emerged as a spin-off from the original Half-Life game, going on to become one of the most popular online PC games of all time.
It pits a gang of terrorists with a particular aim against a team of counter-terrorists whose mission is to stop them within a defined time limit.
As a game, Counter-Strike: Source will be familiar to its thousands of fans, as it has remained essentially unchanged.
Instead Valve has used Source to overhaul the game, with better-looking worlds, more realistic weapons and much more life-like movement.
Half-Life 2 could be out in the coming months
"During the actual gameplay, the introduction of physics provides for a much more visceral experience," said Mr Lombardi.
"And small graphic details such as shadows change the gameplay on the tight, atmospheric areas of certain maps.
"We also plan to experiment with new gameplay types derived from the physics simulation system."
Part of the aim of Source is to create a virtual world where objects react as they would in the real world, with the same physical attributes such as sound, buoyancy and friction.
Valve hopes this is one of the elements that will set Half-Life 2 apart from other games, with players able to use objects around them as weapons or for shelter.
But Mr Lombardi admitted that this may be as real as games can get.
"In terms of visuals and sounds of the software playable on today's hardware, yeah, I think we're approaching a point of diminishing returns.
"However, I do think the hardware will evolve to offer more advanced 'surround' display units, and perhaps more efficient input devices, like true voice input, and the introduction of these would naturally open the door to new experiences and designs."