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- https://www.rockpapershotgun.com/2016/10/03/marc-laidlaw-half-life/#more-402769
I think it's really interesting that Doom and Halflife basically have the same plot, except replace demons from hell with alien monsters.
Shady government black-project corporation experiments with teleportation
Some shit goes wrong, portals are opened, hellspawn/aliens swarm over the facility
One guy has to fight his way through, find the portal, go through it to their home dimension, and shut them down (Source)