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Quantum Capacitance: Overcharge it anyway.
Remote Detonation: Kill a Barnacle with a Satchel.
Unified Coupling Theorum: Help the Barnacle and Headcrab find true
love. [0/10]Permeable Infrastructure: Use the alternative path in the Office
Complex.
I'm having trouble with these four in Black Mesa: Source. I have already completed all the other achievements, but these have stumped me.
What exactly is a Barnacle? Do they mean Headcrabs? I'm very confused.
Best Answer
Quantum Capacitance
Hold the secondary fire button of the Tau Cannon weapon (right-click, by default). The weapon will then overcharge if you hold it for some time (you will know this as your health and shield will take a hit).
Remote Detonation
This is a barnacle
And here is a satchel charge:
Kill one of the former, with the latter.
Unified Coupling Theorum
Lead a headcrab to a barnacle's tentacles and have the barnacle eat/kill the headcrab.
Permeable Infrastructure
There's an alternate route through the vents in the Office Complex chapter. You need to go through that route to get this achievement. See this Youtube video on how to find that route: