When it comes to real-time strategy games, there are usually two main gameplay modes: the single-player campaign, where you play through a series of missions and experience the game's story, and the multiplayer, where you play on balanced maps against an opponent with access to the exact same resources as you.

However, if you wanted to play cooperatively with a friend, at least in the case of the hugely popular StarCraft, you could only do so by playing a team multiplayer match—two versus two, three versus one, etc. Aside from taking turns at the keyboard, there was no way to play the campaign and experience the story together.

That all changes thanks to the StarCraft Co-Op Campaign Mod from the two-person team of "TyrZ" and "r4z0r84." The mod—which we should note is for the 16-year-old original StarCraft, not its 2010 sequel StarCraft II: Wings of Liberty—makes it so two players can cooperatively play through the entire game's campaign. Each player controls their own army while working together to complete the game's objectives. (Think of it as the difference between playing Team Slayer and doing a co-op campaign in Halo.)

For non-base missions where you play through a somewhat linear path and complete objectives rather than setting up a base and expanding out, triggers such as unit-replenishment and cutscene-activation have been scripted for two players so that events happen dynamically, especially depending on the skill and choices of your partner. Base missions provide a unique new challenge, too, as they will not always spawn players near each other (which would prompt the decision to build a singular, defensible position). Sometimes players are spawned on opposite sides of the map, requiring coordinated, long-distance efforts to defeat their common foe. Also, difficulty has been scaled up to compensate for twice as many players fighting their way across the battlefield.

Currently, all three campaigns (Protoss, Terran, and Zerg) have been completed for the base "vanilla" StarCraft game, along with the Terran and Protoss campaigns from the game's expansion pack StarCraft: Brood War. (The latter of which launched just over a week ago.) The Brood War Zerg campaign is currently under construction.