Users of the ResetEra portal noticed that two Valve employees' LinkedIn profiles mentioned an unannounced game they had been working on since 2021, which is described as "an ambitious game with never-before-seen gameplay." These are the profiles of former company designer Michael Anderson and artist Boyang Zhu.
The game has several prototypes, including puzzles and AI NPCs, but it's unclear what kind of game this is, since it's unknown what happened to Neon Prime, which was never officially presented.