The original Portal was almost an afterthought, a bonus game for those who bought The Orange Box mainly for Half-Life 2 and its episodic extensions. However, the first-person puzzler was so addictive and ingeniously paced that it ended up overshadowing the headline acts - for some at least.
This time around, though, the sequel is the main event, and takes the concept to a whole new level.
The idea, for those who haven't played the first Portal game (and if you haven't, we advise you go straight out and buy it immediately, as part of The Orange Box or stand-alone from one of the many games-on-demand platforms), is that you progress through puzzle rooms of progressive complexity by creating portals in walls and floors that you can travel through.
It relies on lateral thinking in three-dimensions, as you have to work out how to get to switches that are seemingly beyond your reach, or how to traverse fields of armed security drones without being frazzled.
However, because it was merely a bonus game, it is also criminally short. And that's where Portal 2 comes in.
Valve has listened to the fans, and addressed several areas. For starters, the first game didn't have much of a plot. You were a test subject for the Aperture Science Computer-Aided Enrichment Center - a human behaviour research facility - and had to progress from one level to another as, essentially, a guinea pig (although there's a cool, scripted ending that's also referenced in the sequel).
In Portal 2, however, you can immediately see that things are different from the tutorial levels. Rather than the clinically stark surroundings of the first game, the Aperture Center has been left unattended for some time, and is in some state of disarray. Some equipment still works, but it's all overgrown with plant life, and many of the features are crumbling or broken. It's up to you, therefore, to find a way out. No easy feat...
Thankfully, you have a helper in the guise of Wheatly, a small, spherical robot that's voiced by The Office co-creator Stephen Merchant - who has a distinct Bristolian twang, and as such gives the ambience an altogether British feel. His presence also aids the narrative of the new title enormously, and adds a new level of comedy that's more obvious, but no less enjoyable than the original's darkly humorous satirical training instructions.
Certainly, during Pocket-lint's play with the demonstration levels presented to us at Electronic Arts' Spring Preview event, we laughed out loud several times. And, as we were wearing headphones, we attracted a few strange looks along the way.
The other thing we immediately noticed was that the levels seemed larger in scope, and offered much more variety in gameplay. The first, for example, doesn't even outfit you with a portal gun, instead opening apertures through the pressing of buttons, for which you have to work out a sequence.
There's also a lot of levels in darkness, and you finally get to see areas of the Center that were restricted before, such as maintenance tunnels.
Needless to say though, especially for those who have played the first, as soon as we started, we didn't leave the demo until we'd finished every preview level afforded us (about nine or ten in all). It is, like its predecessor, impossible to put down.
EA had both Xbox 360 and PS3 playable demos on site, and in our brief look, both seemed identical (maybe the Xbox 360 version just shaded it on crispness, but it was very very close).
We didn't get to play multiplayer sadly, and can't wait to try the new co-op mode. You'll have to wait for our review to find out what we think of that.
Portal 2 will be out on Xbox 360, PS3 and PC on 21 April. And, from what we've seen already, we cannot wait.