FreeOrion is a free and open source community-developed 4X turn-based galactic empire strategy game.
Version 0.4.4. There are a lot of features and possibilities that only tend to become clear while playing a campaign right through to the 'end'. The 'end' is user-defined as victory conditions have not been implemented yet. There are a lot of types of spaceships and plenty of equipment to build numerous vessel just the way you want them. The number of buildings that can potentially be build is pretty big too. Pop-up windows keep... popping up and window settings are not saved. Still, there are many options to customise the user interface, video and audio settings as well as game play parameters. I have rated support in the middle as "Just OK" as I have not yet contacted them. Read the included Wiki for pre-requisites information about buildings and ships, and about planets, stars and blackholes. Check for the focus on the right hand side planet panel when starting new construction.
A good concept well executed. A though-provoking creative game. The only down-side I see is that sometimes program can appear to stall when doing a lot of work, such as at the beginning of a turn or when reordering the build list items, but faster processors and continued work in this area can reduce how noticeable this effect is.