I'm gonna try to beat Half-life without killing.
Rule 1: I can only kill if necessary to progress, like nihialanth, gonarch or tentacles.
Rule 2: Npcs can kill each other, that means that barney's kill count is going up.
Rule 3: i can use bugs, bugs like the one to skip we got hostiles or the infinite health one that sometimes dosen't work and gives me infinity armor. 50/50 chance of working
Gonna update my progress in the comunity or in the comments of this post.