:It doesn't necessarily have to be open world as is currently used these days. The OG Doom isn't exactly linear, but also isn't open world in any sense. Remove the loading times between levels and it would be open world in the way that term was originally used. The desirable aspect of an open world, for me, has more to do with the continuity of the play space than how games calling themselves open world games are designed. Free to explore the map without it just being a series of hallways with only one actual path and maybe 1 dead end per fork where they stick a "secret" or treasure.