Myamoto's interview on gamasutra about mushroom-related game design. They have a very interesting point:
The big challenge was the connectivity. Our question was, "How do we use the Game Boy Advance screen, and how do we use the GameCube screen, and find a way to make that fun?" The best example I have of making it fun is actually a very simple one. Basically, a giant bomb will fall onscreen on the GameCube, and there'll be this giant bomb sitting out there, and a timer starts counting down. And essentially, anyone who's still on the GameCube screen when that bomb goes off, it's game over for them. And so at that point, what those characters have to do is they have to find a hidden hole or passageway that will lead them down to the Game Boy Advance screen where they can take shelter from this giant bomb. So essentially it becomes almost like a hide and seek game. So that's a very simple example, but yet it's something that couldn't be done without the two screens connected, without connectivity. So for us, the hard part is not simply forcing the gameplay onto two separate screens and saying, "We have two screens, so at this point let's make them go down here, and at this point let's make them go up to the GameCube screen, and oh, over here they can go back down to the Game Boy Advance, and over here, let's just make them go over to the GameCube." It's about taking that connection and finding a way to take advantage of the fact that you have those two screens, and turn into something that's fun to experience. And so that's what I think is the big challenge, which is to come up with those ideas that make the connectivity mechanism fun.
The interview also put forward the revival of cooperative play against competition! Finally! Here could start lots of work about players' behavior while cooperating!
JM: Lately, there's been a renaissance of cooperative play, as opposed to competitive play. What were your feelings about creating a game driven by cooperation?
EA: The thing that I think is interesting is that cooperation is actually a different style of gameplay, and gives a different response than competition. The thing about Four Swords that's funny is that although it's a game that four players have to cooperate to solve puzzles, when you play it four-player with three of your friends, you actually end up competing a lot more in that game than you do cooperating. Because they're all cooperating to solve the puzzles, but then they're all racing to be the first one to get treasure, and items. So they end up fighting each other a lot. The thing that I think is really fun about that game is the shift between cooperation and competition, and how it can just turn suddenly, where you're cooperating, and then competing, and cooperating. It really makes for a really different interactive vibe between the players, and a very different environment. I think a lot of people are going to sit down to play, maybe not expecting that, and realize, "This is really fun!" [Laughter].