I know this was part of the Humble Survive this Bundle, But still seems a decent price if you missed out. You also get a mystery game as well/ Price is £3.79 + Paypal fee (a lot seem to be doing that these days)
Anyway, if you missed out and wanted to give it a whirl, I think this is worth a bash.
**Free Game Info**
What is +1 Free Game?
By purchasing Space Engineers you will receive 1 Hot Random Game for free. What is Hot Random Game? A Hot Random Game is a random game that worth from £2.27 upto £45.5 on Steam. Hot Random Games are picked randomly by the system and the chance of winning triple A games are %10.
Early Access Game
Note: This Early Access game is not complete and may or may not change further. If you are not excited to play this game in its current state, then you should wait to see if the game progresses further in development.