Nullstar.io is a massively-multiplayer asteroid-style game set in a large Slither.io style world, just like StartBlast.io. It's a fun casual game that is easy to pick up. There are no complicated menus or ship upgrade paths. It is free to play, with no download or registration. There are multiple servers online and players can join from anywhere in the world. You can also play in a solo practice mode vs AI ships. There is no sound.
Use keyboard controls (WADS or arrows) to steer your ship through a dangerous asteroid field. Collect "stardust" crystals to power your ship. Destroy the asteroids (using the Space bar or Shift) to release more stardust. Hyperspace away from danger using the H key.