While giant mechanical beasts are cool, the heart of Horizon is Aloy's quest to uncover her true identity. Aloy has no mother, which makes her an outcast in the Nora tribe, a matriarchal society that prays to an all-knowing goddess.

The identity of Aloy's mom is the singular mystery driving Horizon's story.

"As we were exploring this world, as we were imagining the societies that would come into existence, one of the social orders that we wanted to explore was the matriarchy of this tribe," Gonzalez says. "This ended up being an inspiration for Aloy's character. Because if you have a tribe for whom parenting and in particular motherhood -- bringing forth life and nurturing it -- is the holiest act, the most sacred act that someone can perform, then it would be uniquely painful to not know who your mother was or where you came from."

Along her journey, Aloy becomes a skilled hunter and warrior, and she is placed on a collision course with events much larger than herself.

"We wanted to combine the personal and the epic, and hopefully by doing that, not just satisfy the curiosity of the player, but also provide a really emotionally powerful experience as well," Gonzalez says.

The team at Guerrilla Games studied various societies around the world and dived into anthropology textbooks to get a better sense of how a matriarchal tribe might operate. In particular, they drew inspiration from Jared Diamond's book Guns, Germs and Steel: The Fates of Human Societies.

"It has this idea that one's geography is destiny, in a way," Gonzalez says. "The material conditions in which a group of people are living really determine the technologies that they're going to develop. We tried to use some of that in imagining these groups."

Aloy's world is filled not only with sprawling valleys, flowing rivers and craggy mountains but also with a wide variety of robot-like animals. Their place in the ecosystem is a mystery. Tribe members mention that they don't know where the mechanical beasts came from or what their purpose is.

The Nora tribe and these robotic animals live in a tense balance. Many of the creatures are hostile, and the tribe members often hunt them down for parts. It's a stark contrast: Aloy wearing furs, leather and feathers, hunting shiny mechanical animals that stalk her with glowing eyes.

This play between technology and nature isn't an accident.

"If you look up the definition of nature, it is essentially whatever humans don't do or make. Which falls apart on the face of it, because we are obviously part of the natural order," Gonzalez says. "We arise from nature the same way as any other organism. In some ways, I think the concept calls into question whether or not those two forces have to be opposed to one another."

Gonzalez and Guerrilla Games aren't trying to force a didactic message about nature, technology or motherhood onto players. These ideas are simply the foundation for all of the game's action, suspense and emotional depth.

To that end, one element that Gonzalez helped implement in Horizon is the Flashpoint system. At certain points throughout the game, players can decide how Aloy will respond to a situation, whether with confrontation, compassion or an analytical kind of insight. These choices can end up affecting how the game eventually plays out.

For example, when Aloy is a child, she encounters a sneering young boy from the Nora tribe who throws a rock at her head. She picks up a rock herself and players decide whether she throws it at his head, at the rock in his hand or if she drops it.

"There's a moment later on in the game where you're going to encounter that same kid, where he's grown up, and what you chose to do is actually going to be reflected in the way that that interaction plays out," Gonzalez says. "The way we looked at that was, it's not so much choosing what you want to do, but actually a moment of pausing to empathize with Aloy. It's like choosing how she's going to express her personality."

Guerrilla Games' focus was always on crafting a compelling story, Gonzalez says. And from the very beginning, Horizon was going to star a young woman -- early concept art features expansive landscapes and the tiny image of a girl sitting on a mountaintop or surveying the valley. For Gonzalez, it feels as if Aloy jumped out of the concept art and demanded to be the star of the game.

"It's the kind of thing that Aloy would do," he says.