In 2123 the first true nanite was used, it was a medical nanite that cleared the blood system by removing build-ups of hardened materials. It targeted specific materials, it was contained within a specific environment and it had enormous application to a population that had grown steadily older. It was an outstanding success and was quickly brought online to the public. The success triggered an enormous investment into nanite research and a golden age blossomed. By the year 2300 the world was much cleaner, the oceans were recovering with life, the moon had been fully colonised along with a growing orbital presence, plans were afoot to colonise Mars (special nanites were developed to not only terraform the planets eco-system but to allow men to survive better). The average age of a human had grown to over 120 years. Poverty, disease and famine were on the decline. This is the starting point of the Mechanoids. A special branch of nanite research discovered a way to create nanites that could strongly interact with the atomic crystal lattice of metals, with the careful application of energy and force at a molecular level it was possible to give metals a degree of flexibility and resilience that had enormous potential. The result of the research was what became commercially know as 'flexible metals', and more advanced forms evolved into 'living metals' and 'liquid metals'.
What resulted was called the 'Robotic Age', replacing the Technology Age which had lingered on for quite some time. Nanites were developed to manipulate metals that revolutionised labour and mechanical work and lead to the introduction of truly amazing robots. But this still required a human to run it, robots could not think for themselves, or be creative or respond to unforeseen events. The final breakthrough (although various forms and theories of this technology had existed for hundreds of years) came with the invention of the 'Crystal Matrix', which used light stored within a crystal environment to store knowledge in vast quantities. A Crystal Matrix the size of a penny could hold the complete knowledge of the human race. And better yet the matrix crystal was able to absorb light and convert it to energy, allowing it to function at a minimal level without an external power source. Nanites needed only small amounts of energy to trigger their activity so it was inevitable that the two technologies would mix.
In 2265 the first cybernanetic master crystal matrix (CMx2) was activated on an orbiting laboratory in a sealed environment with a nuclear failsafe (although it had been pointed out that such a failsafe would have next to no effect on most of the nanites involved and would more likely provide them with sufficient propulsion to leave orbit and rain down on the planet). The Master Crystal was able to function with a capacity equal to that of a well trained monkey, adapting to changes in its environment, learning and recalling from learned experiences. With the correct programming it could perform upto moderately complex tasks and communicate at a speech level equivalent to a 10 year old child. Testing of the CMx2 remained in the sealed environment for 10 years due to the paranoid fears of the planetary authorities. The technology and sophistication of the CMx2 was improved and developed further and as a test a CMx2 controlled space probe was launched from lunar orbit in 2297 to travel to Titan, the largest moon of Saturn. The probe arrived (as planned) on new years day of 2301 and sent the now famous message back to earth "HAL wishes all the citizens of Earth a happy new year from Saturn, 2301".
The success of this mission allowed CMx2 technology to be released and so began the 'Cybernanetic Age". The CMx2 was developed and commercialised until it became such an integral part of the human civilisation that they could not survive without it. This is where our story ends, with the removal of the human race and the beginning of the "Mechanoid Age".
Man is gone, vanished from the world. All that remained are the machines. Why the human race vanished can be apart of your story that remains to be discovered, or it can simply be a fact. There are plenty of ways the human race can vanish from the planet quite quickly:
Genetic plague - someone unleashes a plague so virulent that it kills the vast majority of the human race, leaving insufficient numbers to continue. This scenario allows humans to remain in small numbers, possibly returned to a more primitive form, or as isolated communities. This has the advantage, game wise, of leaving most of the infra-structure intact and able to be exploited by the mechanoids.
War - humans unleash a war that destroys them, and most likely most of the civilisation, the remaining world would be a ruin and a dangerous environment for the emerging mechanoids.
Exodus to the stars - the human race has left, leaving behind them everything they couldn’t fit onboard. Most likely a small number of humans remained behind (there are always splitters) but with time died out. Why did they leave? Perhaps they discovered the sun was going to turn nova, in which case your campaign can have a clear end point.
An astronomical event - a super large meteor finally crashes into the earth and destroys the ecology. Some part of the planet is a complete disaster zone, the rest is buried beneath vast dust layers. Only the strongest and meanest have survived. Your game would start some time after the impact, when the planet has recovered somewhat and the dust has settled, allowing light to get through.
Evolution - the humans find a way to transfer their sentience into the CMx2 and do so en-masse, but something goes wrong and with time the human part of the new creation fades away, leaving behind the mechanoid sentience.
My preferred reason is nanite mutation, where the nanites that have become the greatest achievement of the human race are turned against them by some madman, or some natural mutation occurs in the nanites that turns them against their creators. The human race is wiped out almost overnight leaving their machines behind. With time the mutated nanites continue to evolve and finally gain true sentience.
There are a number of places that you can run a game of Mechanoids, although in nearly all of them I tend to remove humanity completely.
The Earth, or more likely a city somewhere on the Earth. The degree of ruin will depend on the way the human race vanished and the amount of time your game is set after that event. It should be between 100 and 500 years because after 500 years there wont be much left except the Pyramids, modern structures are not made to last. A ruined earth has the advantage of plentiful resources and probably an atmosphere.
The Halo is the collective remains of what the human race had placed in orbit around Earth, a vast array of space stations, asteroid habitats and other devices. A huge technological junkyard that would probably last far longer than anything on the surface. Remember that robots don’t need air, but they might need fuels that would normally be obtained from an atmosphere.
Earth is hit by a very large asteroid and the planet fractures and explodes, turning into an area of asteroids that will slowly begin to drift apart. The moon would probably drift away slowly as the earth's gravity dissipates, maybe taking some parts of the earth with it. Possibly for a time a asteroid bridge between the bulk of the earth's remains and the moon would exist, slowly stretching out as the moon moves further and further away. The remains of the earth would also begin to scatter, drifting away from its original orbit and beginning the start of a new asteroid belt. Larger masses might remain that will have sufficient gravity to maybe start a new planet's formation, or maybe the moon will become the core of a new world, but that is a long, long way away. Humanity is unlikely to survive but maybe some do, certainly they would see the event coming and maybe prepare for it. Most likely the survivors will be on the moon, or in space platforms sufficiently far away from the doomed planet. The detritus of earth will remain for the Mechanoids however.
A Generation Ship is a slower than light spaceship dispatched to a nearby star system. It will take generations of human lives to make the trip so usually the human cargo is placed in cold storage and awoken once they get near to their target. In this scenario the humans may have left the ship in the hands of the robots, or they may have already been disposed of by the robots. If they (the humans) still exist perhaps the robots have split into "save the humans"/"slay the humans" factions. A sealed environment has many advantages in a RPG and this more than any other environment might be what you need. A generation ship would have very limited resources, what you have with you is all you have, however it might be possible that special collection ships have been included with the mother ship that allows for the harvesting of materials from deep space (asteroids, dust, wreckage even!).
Generation ships cant stop, they will use a RAM drive to propel themselves to the highest speed possible, then flip over and decelerate to arrive at their destination. There is no room for variations. Accordingly encounters with things along the way will have very narrow windows for interaction, and this in itself can be used to make the adventure more interesting.
The moon has become the dumping ground of the human race. Radioactive dumps, toxic waste, dangerous goods of all kinds, and human trash have all been dumped to the Moon where the nice clean Earth people can forget about them. At the same time mineral wealth from the lunar landscape is gathered and fired back to earth via linear accelerator launchers. An economy based on survival and a frontier based on pure anarchy, not to mention the most hostile of environments. Humans have a role in this scenario but it is the Mechanoids that stride the surface. This scenario will be expanded in more detail in one of the appendix to the game rules.
The three laws of robotics proposed by Isaac Asimov have become a reality, but the CMx2 has replaced the positronic brain. However in this world the three laws are not absolute, and in fact it will generally be the players enemies who break one of more of them. Of course if there are no humans remaining then the three laws become a bit mute, nonetheless they form the basic structure that Mechanoids create their society around. Replace humans with mechanoids and you have a strong set of societal laws, a sort of ten commandments in 3.
A robot may not injure a human being or, through inaction, allow a human being to come to harm.
A robot must obey orders given to it by human beings, except where such orders would conflict with the First Law.
A robot must protect its own existence as long as such protection does not conflict with the First or Second Law.
Of course the new laws need not be so hard and fast, they can be moral guidelines. Obviously a Mechanoid that breaks one of the three laws is either insane or simply not a Mechanoid, and thus is not protected by them.
GMs can use the three laws to test the players sanity (integrity), asking them to make SP rolls every time a player decides not to comply with one of the laws. Breaking one of the laws becomes a 'sin' and should be punished as such. Or it can just be an inconvenience.