Has anyone had experience with this? The only thing I could think of that has come even close to this is Age of Wonders...but that was turn-based, not realtime. I had this idea for a game that I am designing...although note that I don't have any team yet. I think it would be neat both from an economic point of view (resources only found underground), and from a strategic point of view (civs can "tunnel" around the map, popping up behind an army, in a town, etc. What do you guys think about this idea?

Two RTS games which I remember having layered maps are Earth 2150 and Armies of Exigo.

In Earth 2150 you could access the underground through special buildings and you were able to make tunnels with your worker units. While it's true that this provided you with more strategic options, at least in my opinion it was not implented that well. The tunnel building was rather slow and just wasn't worth it.

I haven't played Armies of Exigo so I can't speak much about it (though I'm downloading the demo atm). I'll write more about the dual-layered maps after I try the demo.

Dragonshard has an underground layer you can access through special buildings/caves. The underground layer is a forgotten city that you can lead your heroes into hack and slash RPG style to collect gold and various powerups. There are also multiple entrance/exits so you can use it to get across the map secretly.

In Tiberian Sun (the red alert sequel) there were units that could tunnel which made for intresting (although usually insanly unbalanced) tactics.

Alan

From a tactical point of view I think its a great idea. Underground shelters, tunnels, etc have historically given the US military the most difficulty in controlling an area. Perhaps you could include whether the tunnel, installation etc is successful dependent on what terrain is above it? For example underground is not feasible in marshy places or areas that have rock slabs. If you have opposing forces "popping up" you may want to check out some of the unit histories during Vietnam and especially check out some of the memoirs of Vietnamese generals now available.

Yeah....I am afraid I know very little about engines and programming (I am only skilled at game design and writing, mostly) so I was also wondering, how easy/hard is this? Since it is such an awesome idea for tactics, why has it appeared in so few games? My only thought is that it must be too hard, in some way or another. Either from a programming side, or else possibly from a balance side.

I'm a newby programmer myself, just struggling with the basics. However, from other games I have seen It would be possible to run 2 levels at once. For example; with Sims1 multiple subjects could be operating on both the first and second layer of a house. The 2 levels were seperate programming wise requiring portal calls for subjects to enter and exit them (stair objects would trigger the portal calls) but actions continued to be processed for both levels in real time. It would certainly be possible for tile based coordinates. I hope you can find a programming guru to help you out.

I'd say that probably the major issues are interfaces and balancing. It'd be annoying at best to be continually swapping between different layers of the map, but you can't display two layers simultaneously without running into potential issues with selecting units (which unit do you select if one is visually on top of another?). And for balancing, it's just another level of complexity to deal with. Just how powerful is the ability to move underground? What should it cost? How fast should the units move as opposed to aboveground? Et cetera.

It's certainly doable - the problems lie in doing it well.

Well, I already solved the problem of the GUI, at least, I think I have :P

Basically the minimap would show the aboveground world, and then the underground map would show as a shadowy edge around the bottom and right of the aboveground. Then if you click on the shadow, the minimap changes to the underground map, and vise versa.

It's not just switching maps.

It's things like alerting the player that a unit is under attack. Allowing the player to quickly see where units are in relation to each other even though they're on different maps...

RTSes are [imo] often too "busy" as is. Adding another dimension of relations adds to that while adding dubious gameplay value. [imo] adding more dimensions is better on one map, ala Total Annihilation or Homeworld [though even those were of dubious gameplay value imo]

Another game you may want check is Metal Fatigue. It had three layers: ground, subterranean, and sky/orbit. I don't know much about how they worked together though.