I know it has been mentioned before, but Noctis is an amazing piece of software. It turns you loose on a galaxy with something like 70 million star systems, each with its own planets (up to 40 of them!). Each planet/star can be explored, named and documented. You can then send these descriptions to the website via an "outbox" file, and download an "Inbox" file containing data on star systems that have already been explored by other players.
Even though the galaxy is randomly generated (which is why the entire program is so small), the randomizing seed is the same for everyone, so everyone is in effect exploring the same galaxy.
The game is very low-res, because it runs in old DOS 320x200 VGA, giving it a dreamlike feel. The 3d engine was programmed from scratch by the dev, making the visuals completely unique to any game I've ever seen. It includes light halos, lens flare and water reflection, impressive considering it was written in ASSEMBLER!
I think it is as close to Zen as a space sim can be.