Steam Community :: Guide :: How to use Tripmines in single player
Surface Tension - Half-Life Guide - IGN
Apparently if you destroy the ratman's room in gm_construct 13 beta (after destroying the chair in the dark room and making the stalker go to the submarine room) , it will become
Half Life 2 - Update 28
Half-Life: Alyx - Internet Movie Firearms Database - Guns in Movies, TV and Video Games
Questionable Ethics - Combine OverWiki, the original Half-Life wiki and Portal wiki