The indie attributes its success to Space Engineers use of "real world science, physics, and engineering" with just enough science fiction. It now supports multiplayer.
A survival mode has also been patched in recently for those who want a challenge instead of having full creative mode to do what they want with no consequences.
"We are very excited to celebrate this milestone with our fans, whose encouragement and active participation made this possible,” said Marek Rosa, founder of Keen Software House. “As an independent developer, finding an audience of this size, with this kind of support for our game – even while the product is still in development – is incredibly inspiring."
"The fans, with their limitless ideas and passion, continue to push us to improve, add features, and develop innovations that our community deserves.” Space Engineers launched on six months ago for $19.99 / £14.99.