Go upstairs towards the three doors. When the lights turn off, use your flashlight and immediately go down the stairs into where you shot the orange buttons. If done correctly, you will hear a hit noise on you and the screen will turn black for several seconds. The screen will return and you can see again. When you try to go back upstairs, you still do not get caught; you will have to restart to continue.
From the main menu, select "Configurations"< then "Controls". Find the sentence "Use voice communication" then set "V" as the key to bind it to. When you display the console window, you can now type on it.
Type map c0a0 at the console window to start on Half-Life with the Half-Life: They Hunger weapons instead of the normal weapons. Some of the enemies are also different. For example, Gman is now the Sheriff. The Scientists are now civilians. Barney looks different, and the head crab zombies are now zombies from Half-Life: They Hunger. While playing in this state, the game autosaves when it touches a autosave trigger. The voices are the same. For instance, the endgame level on Half-Life with Gman is the Sheriff, but Gman's voice plays on the Sheriff. Note: The Houndeyes on Half-Life are now zombie dogs, however they still use the Houndeye weapon that produces an electric field.
Go to the point where you see the pilot, then go onto the helicopter before the last two Bosses. Enter the god code in the console window, and drop off where the helicopter is located and find the pilot. While he is going onto the helicopter, kill him. Stay near the helicopter. If done correctly the "Your rescuer has died" message will not appear, and you can continue. When you go onto the helicopter, wait until you stop and go out of it. Look at the cockpit of the helicopter; the pilot is there again.
In the console window , enter the impulse 101 code at the point where you are taken by a zombie bull in a little carriage you cannot escape from. Kill the bull with a strong weapon. Once the bull is dead, you are still moving without a bull taking you.