Update: 10/02/25, 11:29 UTC - Turns out this was actually already a rule that Valve had (thanks SteamDB). It was listed on their Pricing page but this change has made it a lot more visible with its own dedicated section. Still, good to have a reminder this awful practice isn't allowed on Steam. Original article below: Valve have updated the developer guidelines for releasing a game on Steam, making it clear that the scourge of mobile gaming advertising-based business models are not going to work...