At The Game Awards, Shadow Complex Remastered was announced by Chair Entertainment as free and available right away on the official website (opens in new tab). For the uninitiated, it's the PC release of a former Xbox 360 metroidvania game released back in 2009.
Shadow Complex was met with favorable acclaim back in the day, though who knows how it's aged. I remember playing Shadow Complex and enjoying it. Either way, there's some exploring and upgrading to be had, and free is free.