Xenonauts! If you played X-COM: Enemy Unknown or X-COM: Terror from the deep and liked these games. Shut up right now! And go get this game.
It is THE spiritual successor to these games, in a way that UFO: Afterlight/Aftermath/Aftershock never really managed to capture.
10/10 rating, they have started opening up the ENTIRE game code to the modding community, pretty much ensuring that this game will live on for the next 20+ years via whatever mods the rather fanatic community can create.
/fanboirant