Since the release of Half-Life 2: Episode 2 in 2007, Valve has gone through multiple iterations of a potential Half-Life 3. One such idea would've turned the game into a replayable rogue-lite of sorts, after the success of the Left 4 Dead franchise.
The idea, detailed in Geoff Keighley's Final Hours of Half-Life: Alyx, was in development during 2013 and would've added an element of proceduralism to Half-Life. Players would have to navigate a procedurally generated building to save a prisoner and engage in random enemy encounters. More traditional story elements would've been served in-between these runs, but the core principle would be replayability.
The idea was ultimately canned, but not for straying away from the foundations of the series. Instead, this version of Half-Life 3 suffered from development issues with Valve's Source Engine 2, which made development challenging. Source 2 was missing features such as lighting, save functionality, and visibility options, which compounded with the difficulty of modelling outdoor areas in an engine more suited to blocky interior ones. These issues contributed to the cancelation of this Half-Life 3 iteration, as well as a proposed Left 4 Dead 3.
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