This is my unfinished campaign I made for half-life. I couldn't finish this because of my exams but I have made a map for half-life for the first time and this campaign looks promising so I will finish it up later.
You have infiltrated a high security facility and you must use the teleporter at the end of the level. As this map is unfinished, you will only go till you reach the airducts where you can see the sky. If you want to go to the teleporter room, use noclip and go towards the right side of the airducts. There, you can activate a wave where ememies will come rushing towards you can you will get unlimited ammo.
To play, type "map epsilon" in the console.
Installation instructions are given.