Multi-level gameplay
Gamasutra has a Designer's Notebook piece by Ernest Adams centring around the concept of 'multi-level gameplay' -- that is, games with multiple 'levels' of interaction, or different modes of play. An example is the interrelated tactical and strategy modes found in war-games: you can make decisions that affect the entire world, but also fight individual battles on the ground.
Multi-level games are more complex, but allow you to enjoy different aspects of the game -- knowing that you'll have to fight personally if you move an army to a particular spot makes you feel more involved than if the computer simulates a battle. They are hard to design, however, and balance between the different game modes is key.
Some games implement this 'multi-level' feel slightly differently. In The Movies, you can choose to micro-manage your studio and let the computer generate your films; you can choose to have the computer take care of the studio for you (more or less), and delve into movie-making instead; or you can balance the two. The ability to switch in and out of "director" and "manager" modes is an asset of the game.
Similarly, many MMOs allow a flexible zooming between states and roles. You can play solo, equipping yourself to be as self-reliant as possible, or you can switch to being part of a seamless team -- as tactical leader, group healer, damage dealer or other specialised role -- to defeat bosses or other players. In some worlds you can directly shape the game world and economy; in others, you follow a storyline but feel part of a much larger whole. FPS games have similar options -- the lone wolf versus the coherent team. These all rely on the multiplayer aspects of the game, though.
It ultimately comes down to flexibility, and choice. Multi-level gameplay is about letting the player decide how they want to play, and balance their skill across different game modes. Mastering the macroscopic gameplay may not make you any better at the microscopic, and that's where multiplayer has its strengths, but single player games can learn some lessons from this.
Decision-making also crops up in Adams' Players' Bill of Rights, a list of features he believes "every player has a right to expect". It's an excellent read and many of the points strike a nerve--we've all played games with horrendous cut-scenes, aggressive saving and no pause function, haven't we?
[Thanks, m3mnoch]
