Half-Life: Opposing Force is an expansion pack for Valve Software's science fiction first-person shooter video game Half-Life. The game was developed by Gearbox Software and published by Sierra Entertainment on November 1, 1999. Opposing Force is the first expansion for Half-Life and was first announced in April 1999. Randy Pitchford, the lead designer on the game, later noted that he believed Gearbox was selected to develop Opposing Force because Valve wanted to concentrate on their future projects. Over the course of development, Gearbox brought in a variety of outside talent from other areas of the video games industry to help bolster various aspects of design. Opposing Force returns to the same setting as Half-Life, but instead portrays the events from the perspective of a U.S. Marine, one of the enemy characters in the original game. The player character, Adrian Shephard.
Inspired by a particular "game" that has quite the unfortunate fate, this map basically is a defense map where you have to stay alive for a long time while apache choppers continue to swarm and attack the train you're on.
Quite similar to another demake of mine based from another not-so-fortunate "game" (though that one wasn't good enough for an actual release, a video of it exists though, somewhere).
Watch the roofs, they're not that strong. A solid hit on those and they're toast, and I doubt having nothing to shield you from those unfriendly guests are anything but good.
The map is made with the Hard difficulty in mind, things like the amount of time taken before the next apache encounter shows up will reflect it, keep that in mind when you find yourself waiting quite a bit after taking out an apache group in an easier difficulty.
Additional weapons will be given to you as time goes, and there's also a secret weapon that while may not look as useful, could be a real help at the tougher fights.
Keep your weapons checked between encounters, and your teammates safe.
ADDITIONAL MUSIC FROM:
Chris Jensen - Mishaps In The Reactor Chamber - Opposing Force Unreleased Tracks
Installation is simple. First, ensure that you have Opposing Force installed and ready to go.
Then, extract the z_train folder that is inside the .7z into your Half-Life installation folder (Where hl.exe is located, NOT inside any of the other folder such as "valve" or "valve_hd")"
Example would be "C:\Program Files\Steam\steamapps\common\Half-Life"
There should now be "valve" and "z_train" inside you Half-Life installation folder along with any other
mod/steam-related folders you may have inside.
Restart Steam, "Hold down the Fort" should be inside the Games list.
If that doesn't work somehow, create a shortcut of hl.exe, open it's Properties, add " -game z_train" to the end of the target bar.
Example would be "C:\Program Files\Steam\steamapps\common\Half-Life\hl.exe -game z_train"