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That's right, a prefab with wich you can make your scavenger maps for... Left 4 Dead! With one 4, zero 2-s!

For the sake of irony, let me quote an article on Softpedia:
"As long as Valve makes sure the game mode(Scavenger) is customizable, it should be a blast and will deliver an experience that cannot be in any way replicated in the first Left 4 Dead."

Someone underestimated the modding community... again?

Please note that this prefab requires basic understanding of inputs/outputs and logic entities if you want to customize these prefabs to even the slightest. I've released a tutorial that helps customize the prefab to your map.

This prefab pack contains prefabs for 3 kinds of scavenger mode, for campaign, versus and survival, in order:

1."Campaign" Scavenger - This is kind of like a unique kind of panic event rather than a complete gamemode, tough it depends on the way you implement it. When the survivors arrive(or start out) at a generator, they have to press the button to turn it on. This starts a panic event and causes a single gas can to spawn. The survivors must find this gascan and bring it back to the generator, fuel it in, cause another gascan to spawn, and bring that one back too and so on up until a certain amount is reached in wich case the map is able to be continued and the finale stops, or if they are directly next to the safe room then the safe room becomes accessable and the number of zombies increases and never stops until the survivors make it into the safe room.

2. "Classic" Scavenger - Similar to the scavenger mode in L4D2. It requires a sourcemod plugin of some sort that can add or subtract from each team's score. There is a fixed amount of gascans spawned at random locations at start. When the survivors leave the 'safe area', the panic event starts and they must bring back as many gascans as they can. Each can gives them 100 points. After being turned on the generator can run for 2 minutes before needing a gascan, failure to bring a gascan to the generator in that time will cause the generator to stop and the survivor team to be terminated.
However if they collect all the gascans in the map the game considers that they have completed the map and goes to the next map or switches teams depending on if both teams played survivor or not.

3. "Survival" Scavenger - In this mode looking for gascans is not so important. The goal of the map is simply to survive like usually in survival mode, however the maps for this game mode should be designed so moving continously is an advantage of the survivors, and so they can run around in circles all they want. Similar to "Classic" Scavenger, there are multiple gascans spawned at a time. If they bring back a gas can, they get 20 seconds "peace" time, meaning any zombie that spawns is instantly killed for 20 seconds, and a random item(either some pills or a first aid kit, with the pills having 2/3 and a medkit having 1/3 chance).
After 20 seconds the horde starts coming again, and if there is only 1 gascan left, another gascan is spawned. Keeping to the survivor mode's tradition, as survival mode's difficulty increases the more time into the match, the difficulty of finding gas cans also increases the more gascans your team retrieved.

Please note that the "Classic" scavenger mode could not yet be tested in Versus mode, if anyone can test it in versus and report if it does/does not work as intended, i would really appreciate it.

Other than that, if any of the prefabs don't work as described above, please let me know. I will write a whole tutorial series on using and customizing this prefab.

Enjoy!