Here's the basic setting and plot.
It is the year 2645. The world of the future is a veritable jungle, teeming with new and ferocious forms of life. Many creatures of the Earth have undergone rapid and forced evolution, ever since the asteroid Dalkaron collided with the Earth in the year 1958. This caused worldwide cataclysm, destroying much of society and driving the entire human race to near extinction. At the end of the 20th century, all that was left of humanity's greatest accomplishments was gone like dust in the wind...
In these new harsh times, those who have survived have long forgotten of the lives of what they refer as Archeo-Humans. Every day is another chance of possible death, with future humans having to survive in the new jungles of a strangely primeval Earth. Long after the Dalkaron Collision, creatures similar to dinosaurs began to appear in the biosphere, and other prehistoric throwbacks were also beginning to emerge. The entire western hemisphere(where the asteroid collided) has become a new gigantic ocean called the Titan Sea, where massive undersea predators lurk.
Humans, having lost most of their technology, have reverted to using a new type of gas-powered firearm as their main weapons. These firearms, called Diesel rifles, are one of the only things keeping humans from being consumed by the many predators that lurk in the jungles. Diesel rifles, while crude, are powerful firearms capable of unleashing hails of burning destruction on their targets. The fuel they run on is a a new source of energy for these human beings, one they have dubbed "Diesel X". Diesel X is extremely abundant underneath the surface of this primeval Earth, and it is quite efficient compared to more archaic fuels.
With the world now having become infested with predator-filled jungles, rebuilding society has become a trial for all surviving humans, forcing them to remain as nomads. Rick is one of these many nomads. He is a young and brash teenage boy, part of the Gen tribe, which are one of the many tribes across the world. While out hunting for game, he accidentally falls into a deep pit. Underground, he discovers an ancient(and it definitely WASN'T built by humankind) temple that is seemingly made of rustic metal, and upon venturing deeper, he discovers a powerful and prehistoric robotic device, which is known as one of the many Diesel Walkers. These robots run on Diesel X, and are relatively mysterious and unknown to the humans of this world. They are incredibly strong, capable of taking on many of the massive predators that lurk the primeval jungles. The specific Diesel Walker Rick comes upon he names Diesel Pharaoh, for it's resemblance to old Egyptian hieroglyphs he had once seen in his youth. With this new device in his possession, Rick decides the time has come for his tribe to finally make themselves a place they can call home. As Rick begins to lead his tribe in building one of the first occupied settlements in centuries, he is unaware that across the world, many more Diesel Walkers lie buried in ancient temples underneath the earth, waiting to be discovered...
So if anyone is interested, your role as a character would be one of the many survivors in this harsh new Earth. As a note, every Diesel Walker is practically unique, so Rick's is only one of many. I kind of would prefer teenage characters in this, since Rick is going to be one. Nevertheless, just about any character is allowed, and if anyone is interested in this idea, I will be happy to include you.