This guide assumes you've already successfully installed Opposing Force and imported its maps into Sven Coop. If not, then read this guide first.

Things we're going to fix in this guide:

-Respawning ammo and supplies
-Infinite respawns / no survival mode
-No classic mode
-Final boss doesn't spawn
-No nightvision goggles
-Bonus: custom HUD

Some of the fixes are also applicable to Blue Shift and Decay expansions.
Written with self-hosted listen servers in mind, but it should also work for dedicated servers.

The game offers little challenge when you can just wait around and get infinite ammo, health and armor spawns. The campaign wasn't designed with this in mind, and this behavior is inconsistent with both the original game and svencoop's version of the half life campaign.

In order to fix this, we're going to have to copy some lines into each map's .cfg file. This is a bit tedious, but it shouldn't take more than a few minutes.

1. Right click on Sven Coop in your steam library and go Manage>Browse local files.
2. Then go to svencoop/maps and find the opposing force map configuration files (of0a0.cfg to of6a5.cfg)
3. Open each config file in notepad and add the following lines anywhere, then save:

BUG: Try as I might, I couldn't make weapons respawn, while ammo doesn't. I've tried the "mp_weaponstay 1" in the cfg file, from the server options and "making mp_weapon_respawndelay -2", nothing seems to work - if the weapons respawned, so did the ammo. If you can find a fix for this, write it in the comments and I'll edit this section of the guide. So currently, a weapon DOESN'T respawn when one player picks it up, but that shouldn't be that big of a problem, because the other players will get that weapon on the next map change (probably... if it's added in the map .cfg file).

IMPORTANT!
Because the portable barnacle will not respawn once picked up, you may have problems with the level where it's picked up, where you will encounter a pit that can only be passed by using it. There are several possible fixes for this:
Some of the fixes are also applicable for the Displacer Cannon level!

1. Write "mp_weapon_respawndelay -2" on that particular map only (that's of4a3.cfg) to cause weapons and ammo to respawn. You can also write that directly in the console BEFORE picking the barnacle up.
2. Have one player pass the gap, then drop the barnacle down for the next player to pick up. The default key for dropping weapons is "G", but you can also access it through the commands menu "C", then press "1" twice to drop your current weapon.
3. Have the other players use noclip. Open the server console (~ key) as the host, and type "sv_cheats 1", then have each stuck player write "cl_noclip 1". After reaching the ledge, you can turn noclip off by typing "cl_noclip 0"
4. Just have the one player with the barnacle finish the level, in the next level everyone should have it.
5. Use cheats again to add the missing weapon:
"give weapon_grapple" - Barnacle
"give weapon_displacer" - Displacer Cannon

There are two ways to enable survival mode. Simply voting from the vote menu will tell you the map doesn't support survival mode. So we gotta do some more .cfg file editing, or install a server plugin that forces it.

METHOD 1:
Like we did in the previous section, we gotta add a line to each map's .cfg file:
You can instead edit this line in default_map_settings.cfg (in Sven Coop/svencoop folder) - the default is set to 0. This will apply to all maps you host that don't include the line in their cfg files.

I personally haven't tested this method, but it should work. Let me know in the comments if it does or if there are any problems.

METHOD 2:
There is a plugin that forces survival mode on all maps that you host. You can download it from wootguy's github project called "ForceSurvival"
Link: https://github.com/wootguy/ForceSurvival/releases/tag/v1
1. Download ForceSurvival_v1.zip
2. Go to sven coop in your steam library and click "browse local files"
3. Open the "svencoop_addon" folder and extract the .zip file you downloaded here. The final file path should look like this: "Sven Co-op/svencoop_addon/scripts/plugins/ForceSurvival.as"
4. Enable survival mode by default, by editing ForceSurvival.as with notepad. Find the line
and remove the minus, so it becomes "int g_force_mode = 1;"
5. Now we have to enable the plugin. Go to Sven Co-op/svencoop/default_plugins.txt file and open it in notepad (or notepad++ for better visibility and less chance of errors)
6. Add the following code between another two plugins, then save and exit:

Nice! Now every server you host will be forced into survival mode, even if the map doesn't "support" it. If you want to disable this plugin, simply remove the code you added in step 5 or comment it out (add // at the beginning of the line)

If you'd like to play with the original weapons and weapon models, you'll find that classic mode is disabled for the opposing force maps for some reason. However, you can enable it with another plugin from wootguy called ClassicModeDeluxe.
Link to github: https://github.com/wootguy/ClassicModeDeluxe/releases

1. Download ClassicModeDeluxe_v9.7z
2. Extract the contents into the "Sven Co-op/svencoop_addons" folder
3. Open "Sven Co-op/svencoop/default_plugins.txt" and add the following code like we did for the ForceSurvival plugin:

There is a lot of configuration for this addon, so I recommend you look around at the files in svencoop_addons/scripts/plugins/ClassicModeDeluxe

Currently, the final boss is bugged and does not spawn in sven coop. Luckily, there is a fix for this that you can install.

The fix can be found in CubeMath's github project called UCHFastDL2. There are other good stuff in there, like the nightvision goggles plugin that we're going to install later.
Link: https://github.com/CubeMath/UCHFastDL2/blob/master/geneworm.zip

1. Download geneworm.zip from the github link
2. Extract it to Sven Co-op/svencoop_addons
3. Go into svencoop_addons/maps and edit the map's .cfg files with the above fixes that you've applied to all the other maps. Take care, because the lines you add might already exist, edit those instead of adding them again!

Congrats, now you can finish the game!

You might think that the night vision goggles are in the game by default, but no. You might also think that you'll be just fine with flashlights, but some areas in Opposing Force are designed with nightvision goggles in mind (Voltigore tunnels), and you will not have a good time without them.

The plugins for the goggles are also from CubeMath's github project UCHFastDL2 under svencoop/scripts/plugins/Nightvision.as
Link: https://github.com/CubeMath/UCHFastDL2/tree/master/svencoop/scripts/plugins

1. Download Nightvision.as and place it in "Sven Co-op/svencoop_addons/scripts/plugins
2. Enable it in default_plugins.txt with the following code, as we did the two plugins before:
3. Go ingame and host a listen server on any map. Open the console with the ~ key and write ".nightvision" to test if it works.
4. If it does work, you can bind it to a key for quick access. Write in the console
to bind it to the "N" key.

Step 4 has to be done by all players that want to use nightvision goggles in your server!
This will also work in any other servers that have this plugin enabled.
The nightvision goggles provided by this addon are a recreation of the original and don't look exactly like them - there is no grain effect, and it may be slower to update with your location, especially with high ping. Also it doesn't use the flashlight battery and can be used along with the flashlight. Still, it's way better than nothing.

5. (Optional) If you want to disallow your players from using the flashlight (as they wouldn't be able to in the original Opposing Force), add the following to each map's config file, or change it in default_map_settings.cfg (in the svencoop folder):

Just for bonus flavor, you can download a mod that tries to imitate Opposing Force's HUD, however instead of Commando green, it's in Sven blue. It's been ported by SV BOY, go say thanks! <3

You can find the mod both on moddb and gamebanana, under the name "Opposing Force HUD for Sven Co-op".
Link: https://www.moddb.com/mods/sven-co-op/addons/opposing-force-hud-for-sven-co-op
Link: https://gamebanana.com/mods/download/24822

1. Download opfor_hud.rar
2. Open the archive and navigate to the svencoop_addons folder inside
3. Copy the contents into your own svencoop_addons folder.

That's it.

Thank you for reading this guide. Note that it's written on 28 Feb 2022, and depending on future updates from the Sven Coop team, some of these steps may be obsolete if official fixes for these issues are released. Fingers crossed.

If there is anything I should add or fix in this guide, please let me know in the comments, or via PM.