Having recently bought myself two wide screen monitors purely for development purposes, i began thinking about potential design choices for games which could leverage the users' extra monitors.

I am not aware of any games that use multiple monitors in an interesting gameplay-wise way, similar to what the new consoles are offering with their "LCD screen on your controller" scheme, and having a minimap always shown on the other display (i remember seeing that somewhere).

Note that this shouldn't apply to multiplayer games because you want to have maximum fairness in those, where neither player has an obvious advantage just because they have more money to throw at peripherals, but rather single player games.

The choice also has to be optional because not everyone has more than one monitor, and the game still needs to be playable on a single monitor computer.

If you had the money/freedom/need to design an optional feature for multiscreen setups, what would it/they be? Minimap on the second screen? List of party members? Inventory always shown?

I'm interested to see what different people would do if they had the option. :)

Supreme commander (An RTS game) simply gave you a second camera on your second screen. You could place it over your base/army so you could easily look back there without having to click or use a hot/key, or you could fully zoom out one camera to use it as a mini-map.

I think that's the only game I've seen do this... Others support 3 screens to do super-wide-screen rendering - just one camera with a huge horizontal FOV. That is a fairly big advantage in a shooter game... But you could negate this by allowing any player to turn their FOV up to 110deg/etc - it will just look really silly on a single monitor!

Well the Nintendo DS is a good place to start. All of the final fantasy ports make extensive use of the 2nd screen, in such a way that wouldn't be out of place for computer-based games.

For the most part, it could help you remove the unecessary clutter (UI that is not immediately relevant).

Could also have inventory management open there.

There are a lot of games where inventory and whatnot opens over the game, while the game actually remains active. In this case, you could use the 2nd monitor to handle this.

If you are looking for something more, perhaps in a racing game you could have the rear view in the 2nd screen, or something similar. Would even work for dogfighting games too.

That's all I have though.

I've been looking at simulated cockpits lately, for flight simulators, and one of the configurations that seems appealing is the use of four screens--one a touch screen--to enable the player to use the wide angle while having direct input on the control panels of the simulated craft. That might be a little farther out there than what you're planning on, though.

How about using the second screen as a persistent display of something the player will routinely be bringing up on their screen? Hodgman mentioned Supreme Commander's ability to have two points of focus on the game, but how about the Resident Evil inventory or the GTA map screen or the Arma GPS? These are things that compete with the game for screen real estate at all times, when they really shouldn't have to. Putting them up on a separate monitor would streamline gameplay considerably.

I have been thinking about that too and I got some doubts as a player. I mean, 2 monitors are great for work, but would I enjoy it when playing? Basicly anyone who has 2 monitors has them big, so, it's not feasible to look at them both at once, so for example a minimap on a second monitor would be simply annyoing to me. Also, I like having the second monitor "game free" to check mail, skype, take a quick look if something else does require my attention, etc, etc.

Probably the only options I could accept (with hesitation) on the second monitor would be purely information things, like some "help" open at all times, a library with all monsters, things like that. But for example inventory would be annoying for me (it has to be on the main screen).

In practice I used 2 monitors in one game, I stretched Minecraft window to 2 monitors :D It was quite fun (this huge panoramic view), but I'm not sure I would use it too often.

Another thought, an ingame editor of some sort would be great on a second monitor.

Design wise, I think you just have to be careful that you enhance the experience with the second screen, rather than require it. If you take it for granted, you end up with difficulties when you realize that you've just alienated single-screen users -- its similar in flavor to the kind of problems you experience when you design a UI-heavy program for mouse and keyboard, but then you end up needing it to work for touch-screens as well -- replete with fat fingers and no right click or onHover.

For certain kinds of games, a spectator-style view or stats might work out. Say a racing, sports, or shooter title. I think that for typical PC games, and users' PC-setups, its hard to utilize a second screen for any kind of action -- its just too far away from the main screen to be useful -- it can also be a different size, shape, and resolution from the primary screen, which introduces another set of problems.

Some games feature in-game video briefings whilst the game-play still proceeds; in the Command and Conquer games for example these often temporarily take the place of the mini-map, and I think Starcraft may have done the same thing at a few points during the campaign. You could display these on a second monitor when one is present, and stick with replacing the mini-map for single-monitor systems.

A second map can be pretty useful for strategy games; I really liked being able to have a second map for Supreme Commander, which I would usually keep focussed on my home base in the early game, and would sometimes move to observe main choke-points where there were recurring battles later on. A much earlier strategy game called Alien Nations allowed you to split you monitor into as many view-ports as you liked and control them separately to view different portions of the map -- it would have been absolutely fantastic if I could also use a second monitor to have several views for different uses.