FreeGameDev

Here is the idea:

Imagine a game world where the terrain is folded in 90° angles.
Maybe six sides folded to a cube, but I can imagine even two or three sides "V" or "U" - could work, too.
Of course the twist is: reaching the corners of a terrain gravity switches and you walk "up" the walls as if nothing happened.
So in the end you get a much more vivid gampleay interaction as player contact is more dense while "physically" being far away.
This would open up a huge field of new tactics and mechanics in shooting.

The idea is way over 10 years old, but I still have screenshots of a very early development stage in a quake3 mod I started.
(Back then it was called "Power Hunters" and worked similar to ROTC but with tho goal to capture zones that are connected with energy renewal.)



(spot the tiny player in the middle):

Personalty, I think such gravity gimmicks are cool for single-player puzzle games and for 5 minutes as a novelty in other games.

Why do you think the concept works only in a puzzle?

Because there you have time to think and orient yourself.
In a multiplayer game or when you are being shot at by multiple NPC enemies it is just annoying as the human brain isn't wired to quickly think in the 3rd dimension like that.

Ok I see your point now, and I agree partially.
I guess you're talking about the game becoming a big spawn-kill party - that could become a problem indeed.
Of course you need to adapt to everybody being in fireing range most of the time:
* lower precision of weapons
* make it necessary to have TWO players have a lock to launch disks
* weapons only dealing damage within one plane
* reduce to 2 or 3 planes to narrow down the attack vectors
* ...

Also the "damper/ammuntion - duality" in ROTC is a reason not to fire all the time.