I was considering some ideas that I thought might be fun, and wanted to run one by you: Depth in an RTS seems to be a good idea to me, but so does everything when I first consider it. I was hoping to have multiple layers or depths, much as it is done today. The modern RTS often has cliffs, and elevation differences in the terrain, but everything is still completely exposed to the sky. This makes for some great strategy with height and choke points, but I thought it could be fun to add some depth as well. Here's my implementation thoughts: You have the surface, which is exposed to the sky. There might be various ways to dig, or just go through caves into lower depths that are underground. Some buildings might require two or more depths to be built on (a tower with a foundation that goes underground). Three hotkeys would let you quickly switch between depths (3 depths, max), and there might possibly be three minimaps, or a minimap transparent overlay that shows underground activity. So, would this implementation be the best for the situation? Would this even seem fun to you playing an RTS? Is it worth the trouble?

i had a dream once where 2 sides battled completely underground. The map was one big slab and you had to dig through to get to the other side. As you dug you get resources. This was long time ago when all i could do is built LEGOs but then they stole my idea http://guide.lugnet.com/set/?qc=*underground.

3d strategy is some thing i find fun but i think its better done in a space setting like homeworld.

It's been done, in Metal Fatigue by Zono, there were three different levels: air, ground and underground. It was a fairly fun game, but that was more because of the giant robots rather than the level system which didn't really seem to add much additional depth to the gameplay, IMO.

there was also Armies of Exigo (lol, the site's title has a spelling error in it) which I think was a really solid game, that never got the publicity it deserved and then died a pretty quick death. (No multiplayer platform anymore etc).

It basically had 2 Minimaps always visible and you could always switch between the upper- and lower-level with hotkeys. Problem is: I can't really remember if it actually helped the gameplay and was used extensively in the more popular maps, but there seems to be a single player demo that you could atleast try.

Thank you all, I had forgotten about the conceptual approach.

Tom: Good solid advice. Most RTSs have land and air units, which are conceptually two different planes. Many have water units too, which are on the same plane as land, but restricted to certain units. It definitely is a lot easier to manage than switching between 2 minimaps.

It's looking like this now: Land Units + Air Units + Underground Units. There might be dedicated LvL, LvA, LvU units for example. Not exactly original, but I've finally learned that you don't have to change everything from the ground up to be fun.

Just a quick random idea: how about having a side view? The whole digging underground thing made me think of worms. Off hand, I can't think of an RTS (as in base building and resources) that uses this view. Has it ever been tried?

I can name plenty of turn-based strategy games with underground tunnels, but real-time? Seems impractical and not particularly interesting. As far as multi-level battles go, I thought Supreme Commander did quite a good job of requiring coordinated (land/air/sea) assaults.

Earth 2150 has underground RTS elements. You could create earth quakes and transport troops through tunnels. Seemed like a good idea but the micromanaging was annoying for many units.

I'd say allow players to dig into mountains but not be able to go underground per say. So like mountains in the map might have "entry" regions where tunnels can be started and you can dig out into a tile based grid. Also allow for building in the tunnels and such.

Dragonshard is another RTS that had underground elements.

Their implementation involved set caves that could be entered to move to the underground sections, where the play style was actually somewhat different. It was a D&D based game, so the underground play was giving a somewhat more "quest" flavoured play, where it was a little more like squad-based dungeon crawling than traditional RTS