The guys developing the game Untold Universe are giving away alpha keys. The game itself is similar to Minecraft, but it allows players to build their own spaceships and travel between planets.
Get your alpha keys while they last:
https://www.untold-universe.com/forums/general/topics/alpha-keys-giveaway-official-thread.
A few screenshots from the game (probably not all completely implemented yet at this stage):
PS: By the way, I don't know if this is the right section to post this; so let me know if it isn't.