Starsector, a top down 2D space combat/exploration game which has been described as a cross between Elite Dangerous and Mount and Blade. I would say it is Elite Dangerous on steroids, it is so deep and the combat is detailed and fascinating. At the moment spending more time on watching YT vids on how to play rather than playing as it really does leave it up to your after the tutorial area. Still in development on version 0.951, so still room for extra stuff. There is a campaign story line, as well as the overall sandbox style. An active modding scene as well.