Portal is one of the smartest games ever made. Not just because of its overtly fiendish, inter dimensional puzzles, but the way it makes a complex idea instantly accessible.
Within minutes of holding the Portal Gun, you get it. You understand the concepts of creating doorways and skipping between them, using momentum to propel yourself over obstacles and dropping crates onto switches to open entrances and exits.
It's this considered, yet unobtrusive, design that developers Valve are famous for, and they're doing it again with Portal 2 - the hottest PS3 game announcement of E3. This time, we see more ambition, more insane physics, more puzzles and, yes, more GLaDOS.
Hundreds of years have passed since the end of the first game, and the Aperture Science test centre is overgrown and falling to pieces. Even though you destroyed her core with portal guided rockets, GLaDOS is - like that song so sweetly suggested - still alive, rebuilding the lab to her own demented specifications. That means more traps, more pitfalls, more turrets and more ways to meet a violent end. You still play as Chell from before, although how she managed to stay alive for hundreds of years is one of the game's biggest mysteries.
What GLaDOS' rebuilding of the Aperture labs also means is that there are now a lot more interesting ways to use portals, such as the Excursion Funnel. This glowing blue tractor beam holds anything that falls into it - your character or a turret, for example - in mid air and can be directed around the levels using portals. It's a simple idea, but one that makes for some really interesting puzzles.
Then there are the Aerial Faith Plates, which are a bit more straightforward. Step on them and you're fired into the air as you would be by the spring pads in Sonic The Hedgehog. Each plate fires you in a specific direction, often towards a wall or deadly chasm, requiring quick thinking with the Portal Gun.
Next up is the gel. This sticky substance - which showcases Source's sublime new liquid physics - comes in two colours, each of which has different physical properties and spews from pipes hanging from the ceiling in certain levels. The Propulsion Gel is orange and, when spilled across a surface and stepped on, sends you sliding forwards at rapid speeds. This lets you zip past dangerous obstacles or send objects hurtling through the air to help solve puzzles or hit switches.
The Repulsion Gel is blue and launches you straight into the air when you come into contact with it. In one section of the E3 demo, the gunk is smeared onto both sides of a narrow, floorless corridor and we bounce between them to cross in safety - think wall-running in Prince Of Persia. The physics is incredible, especially when you're moving globules of gel through portals to splash them over surfaces and solve puzzles.
Again, as is often the case with Portal, you have to see this stuff in action to grasp it fully. It's so unlike anything you're used to in games, or reality, and the best way to understand the concepts is to try them out for yourself.
Another new feature, the Thermal Discouragement Beam, is easier to figure out. This red-hot laser can be guided around and you can use reflective surfaces to shine it on switches and open locked doors. It's a variation of a puzzle that's been in almost every Tomb Raider and Resident Evil game, but is made all the more interesting with the addition of portals.