UC3K uses R. Talsorian Games' Mekton and Cyberpunk 2020 game systems. These being chosen for their simplicity, broad-spanning scope and adaptability, ease of learning and availability in .pdf format. And for some other reasons. The main one being that if you are a fan of Mecha anime. I mean shows like Gundam, Robotech, Zeorymer, Detonator Orgun or any of many other titles featuring battle-mechs that AREN'T slowed to a crawl by a pathetic inability to vent their reactor's heat and DON'T maneuver like a pregnant yak, such as in Battletech/Mechwarrior etc. Then you really should play Mekton Zeta. It is such a good mech game system that the Japanese liscensed it to make the official RPG for their Gundam franchise. It is simply the best mech game rule system there is.
The other game system, Cyberpunk 2020 is the single greatest, most extensive, purpose-built cybernetic RPG ever made. With an extensive array of cybernetic parts, options, and even full-conversion kits outlined in it's many supplement books. You can build a cyborg from the most advanced Ghost in the Shell style full-body 'borg to the most klunky, eastern-European, Soviet man-machine with a hydraulic ram-arm made from black market parts stolen from a state factory.
And the impressive array of weapons and munitions will NEVER leave you wanting for more. Literally hundreds of weapons from automatic pistols, revolvers, rifles, shotguns, submachine guns, assault rifles and so on, to exotics like microwave guns, hyper-vibrational and monomolecular knifes, swords and whips, EMP grenades, suitcase nuclear bombs, lasers, masers and tasers, including needlers and gas-powered airguns capable of delivering weaponized bio-chem attacks from impressive distances for an airgun.
There are over 100 vehicles from motocycles to cars and trucks to tanks! Including Blade Runner style VTOL aircars, Osprey Aircraft, and commercial to military planes, helicopter gunships and jets.
And then there's the LandMates and Battle Mechs. UC3K utilizes what I term "Scaled Warfare" meaning that conflict involving your characters will take place in every situation from SOCOM style man-to-man infiltrations and clear and sweep, to Power Armor Mechanized assault using LandMate armor technology. See the LandMate section of this site for full details. Landmates are extremely versatile battle-suits capable of tangling with light tanks and helicopters and personnel vehicles while possessing the small size and versatility to do house-to-house suppression and area-domination.
Battle mechs, as you know are vaguely humanoid war-robots capable of taking on tanks, full helicopter gunships, main battle jets, hardened emplacements and bunkers, naval vessels, star-cruisers and city-warfare. ranging from 20 to 50 feet in height and even larger for the Heavy Mechs, these nearly-unstoppable 21st Century war-machines aren't even the largest of the characters Scaled Warfare options. But they are good for when you just have to kill a whole BUSLOAD of enemies at once!
UC3K takes place in a milieu that is a mix of Masmune Shirow's famous APPLESEED universe and the space colonization setting of the early GUNDAM universe, circa 0079 to 0083. The early Gundam universe is awesomely violent and war-torn, with death around every other corner. See Gundam 0079, Stardust Memories 0080, War in the pocket 0083, 08th MS Team and Char's Counterattack for an example. Your characters will be members of an elite new kind of military unit, the "AP Team" or All Purpose Team. With military resources stretched to the very limits by constant warfare, AEGIS or The Earth Federation combines units from each of it's military branches into 4-10 man teams capable of tackling a variety of tactical and strategic situations. Sort of like TV's "The A Team" where one member is a heavy weapons and mechanical expert, one is a command-tactical officer, one is a pilot etc. Your characters will have access to unprecedented military hardware on requisition, from pistols, rifles and grenades to tanks and jets and LandMates to Battle Mechs. Even effectively becoming command crew of a Star-Cruiser Battleship capable of travel between the planets.
The timbre of the campaign will be war-time space-opera, much like Star Wars or BattleStar Galactica with elements of squad unit tactics like SOCOM or Syphon Filter and so on thrown in too. The upside is that the enemy is a clear and present danger, very similar to the nazis in WWII. They have clearly defined forces and battle lines and you can take the fight right to them in streets, jungles, deserts and even in space.