Quiet Rehabilitation brings a different story of Gordon Freeman being taken prisoner directly to Nova Prospekt. In this alternate route, without meeting Barney, he must find a way to escape from this old facility heavily guarded by Combine forces and surrounded by unusual creatures.
Running a small experiment with a feature I came up using env_microphone entity. In case of a sound issued by the player or any kind of object louder enough, the env_microphone triggers a logic_relay that wakes up all zombies near by.
Each zombie has an env_microphone entity inside them with a sensitivity of 0.5 and a maximum range of 86 that hears combat, world, player and bullet sounds (flags). I also added a few extra ones around it with 128 max range (bullet only) as an initial test.
Pretty slick feature! Wonder why no one has done something like this before!
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Really well done !