All codes from the original Half-Life work here also (despite the map
 name of cause). The cheat mode here can be activated with the command
 line

 hl.exe -dev -toconsole

 and with typing

 sv_cheats 1

 in the console in the game of cause.

 ---

 Hidden door

 Enable cheat mode, then activate the "/map redE3M5" code to advance to
 episode 3, mission 5. Locate the door that does not have a handle
 in that level. Enter the "/noclip" code and walk through the door to
 find another door covered with smiley faces.