If you haven't checked out this game before, now is the time. It's an excellent 4x space strategy game that keeps getting massively improved thanks to the free add on packs, which are basically mini expansions, and has a dev team that actually cares about what the customers want and keeps adding requested features.
Anyhow, it's free to download and play for the next few days (but will have to buy it if you want to play beyond that), and the dev team will be adding new content based on how many people play the game during the weekend, so if it's something you might be interested in, be sure to check it out.