Gravitate is an Arena map. All of the play is in a simulated low-gravity environment, with “vents” that allow players to levitate in certain areas.
In fact, players can’t touch the floor at all! It’s lava! And even the solid ground is so hot that it would instantly kill them.
So the whole game happens in mid-air.
The map isn’t downloadable yet, it’s still in play testing / development.
Here’s an Imgur album of screenshots I took a while ago: