Steam Next Fest is a week-long celebration featuring hundreds of FREE playable demos as well as developer livestreams and chats. Players try out upcoming games on Steam pre-release, developers gather feedback and build an audience ahead of their Steam launch, everyone wins!
I enjoyed it for quite a while. Last I played, the meta gets a bit stale at the higher ratings, but it’s a really great game up until diamond ranking, at least.
I’ll probably buy the full version when it releases.