I recently downloaded Narbacular Drop, the original Digipen student project that was remade as Portal. I have more to say about that, but later. Right now, let me explain what I would do for Portal 2.
It occurred to me that instead of giving the player a gun that could place both the blue and orange sides of a portal, the player could have a gun for the blue side and another character could have the gun for the orange side. Two players could play the same levels, with one having the blueside gun and the other having the orangeside gun.
Having two players share a Portal could lead to a bunch of new kinds of puzzles. Since either player could place their end near them at (almost) any time, splitting up and getting back together would be easy. There would need some way to quickly signal partners with advice and instructions when they are split up (this would be relatively easy with a computer-controlled character). Perhaps each portal-user could have a camera which transmits what they see to a screen their partner is carrying. Also, each player could have an in-game laser pen that could be used to point to where you want your partner to place their end.
Since either player can place and replace their ends of a portal, this may result in mischief. Like Player 1 attempting to walk though the portal, but player 2 suddenly placing his end on a ceiling above some toxic waste at the last second, dumping player 1 in the soup. This sort of deliberate sabotage probably won’t happen too often over the course of the game because players who dislike sabotage can simply split up when this happens. Accidental occurrences of this sort of thing are more likely to happen throughout the game, and will hopefully lead to interesting stories. “Hey, remember that time you dropped five turrets on my head? We almost had to restart the level!”
An advanced version of the guns might allow for the placement of two linked portals. That is: instead of each player having a gun that could establish both sides of a portal, one player would have a gun that made a blueside and a redside, and the other player would have a gun that established an orangeside and a greenside. For reference, I’m calling the blue/orange portal “A” and red/green “B”. This might get confusing, but with sufficient player-training, might be feasible. This would also allow the players to, for example, set up a “safe” portal with an orangeside opening behind a turret. Then a greenside next to some toxic waste. The blue/red player then could step through portal A and put a redside underneath the turret, dropping it through portal B without worrying about where the other player is in relation to portal A.
And, of course, with four portal sides you can do crazy stuff like place an orangeside on the floor, a blueside on a wall, a greenside on the floor next to the blueside, and a redside on the wall next to the orangeside. If the redside is placed so that it knocks a camera off the wall, that camera is going to fall a long way before it stops! Or you could set up a Hyper Fling: fall through the orangeside, come out the blueside on the ceiling which is right over the redside, and finally though the greenside which is on the floor but you have so much momentum you can reach a really tall height.
Even if Valve doesn’t use anything like this in Portal 2, I’m still looking forward to what they come up with.
All Game Design Snippets copyright (C) 2008 Matthew Mather. Source engine used for illustration.