1.It works like H.E.V?
yea and nay.
2.Why yea and nay?
He is more different from HEV of Hl2, at first they can be switched on and off :).
In the second they have a small side-effect-blindness.
Well, they have a purpose detector.
3.If they do not affect the gameplay, because the game is about how the hired killer raskazayvaet your story on interrogation?
No, it is not always possible to turn off or turn them