Novaquark's Dual Universe is a continuous single-shard sandbox MMORPG, meaning that players share an absolutely massive world of potentially millions of players on one server. And the worlds of Dual Universe are fully editable by players. Novaquark's player-driven approach to the game also manifests in the game's economy, politics, trade, and warfare, all of which will be determined by the players.
Dual Universe is almost absurdly customizable. Players can create their own vehicles, buildings, cities, and space stations, but they can also script games, puzzles, interactive constructs, working instrument panels and blueprint apl of their creations to sell on the markets.
Without the usual multi-server setup, instances, or laod times, the game is basically just an enormous persistent universe. There are no NPCs, just other players. The quests will be created by other players who need a job done, the politics are wntirely player-determined, and territories can be claimed by anyone (or any group).
As Dual Universe is basically just going to launch as an empty, uninhabited space to be shaped by players, its an insanely complicated system. It even has physics engines for everything from space travel to underwater exploration, and that's kind of fabulous. It's also incredibly impressive.
I got to sit through a tech demo of some of the game's exploration systems and its various planet, and while there is a very limited number of planets and moons in game, they're all unique which makes exploring them worth it. Which is honestly the hardest task of any sci-fi exploration game. But Dual Universe manages the perfect balance of massive scale and bespoke planetary design.