func_button

Spawnflags

SF_BUTTON_ONLYDIRECT	16 (the button cannot be used through thin walls, which was a known issue in the original Half-Life)
SF_BUTTON_DAMAGED_AT_LASER	128 (the button will be activated when hit by an env_laser beam; see the demo maps)

There is an undocumented feature that makes a button with the SF_BUTTON_DAMAGED_AT_LASER spawnflag set respond to a weapon_egon beam in addition to an env_laser beam. Consider using this quirk to arrange alternative quest routes.