UPDATE 06/07/2016 10.25pm: Turtle Rock Studios co-founder and creative director Phil Robb has billed the developer's countdown as being toward its "Biggest, craziest update yet" on Twitter. He added the hashtag "#StageUp".

ORIGINAL STORY 06/07/2016 9.17pm: Asymmetrical monster-hunting multiplayer shooter Evolve is no longer available for purchase on Steam.

We're not sure why it's gone, though we've asked publisher 2K Games for an explanation and will update when we find out more.

One popular theory is that the game could be going free-to-play. According to Steamcharts, Evolve's userbase has significantly dwindled on PC. Upon its February 2015 release, it averaged a player base of over 9000 simultaneous users, but its most recent month averaged at a minuscule 105 with a peak of 234.

Adding further credence to this free-to-play theory is the fact that the official Evolve website has a countdown timer that will end tomorrow at 5pm UK time.

Despite its shrinking player base, Evolve had a relatively strong launch for a new IP. It was the best-selling retail game in the UK during its month of release and it came in second for US retail sales. 2K Games announced after three months that it had shifted approximately 2.5m copies of Evolve to retailers.