It is a key element of game design to define how best to imerse the player’s experience in the game world. The best interfaces dissapear as the player feels they are just interacting with the game environment. This enables the player to suspend their disbeleif and become emersed in the game.
This obviously has echoes of the interface that Nintendo are trying to achieve with the wii. How often have we heard about the key turning moment in Metroid, that felt so solid and emersive.
There is an interesting case we can discuss in relation to user interface in the recent Yoshi’s Island DS. A key aspect of the game is the ability to throw Yoshi’s eggs across the two screens of the DS. The designers have obviously looked at Yoshi Touch and Go on the DS which had a similar play-mechanic. However they have decided to present this interaction differnetly.
In Yoshi Touch and Go the space between the two screens on the DS did not exist in the game world. This had the benefit of eliminating any dead space that could not be seen bewteen the two screens. However it made it notoriously hard to fire an egg across the screens. You effectively needed to aim a little higher than it appeared to land the shot.
For me this delivers a much more imersive experience, as I am not jarred out of the game world to make my egg go where i tell it. This far outweighs the dead space between screens, as I can still see this space by looking up or down within the game. As put much more concisley by Howard Rheingold:
That part of a computer game that makes the user step outside the game world, that doesn’t help the user to participate in the pleasure of the game, but acts as a tool for talking to the program — that’s where distance comes in.
This approach has now been proven with good sales success of Yoshi’s Island DS: