The story begins with an interstellar fall.
While searching for a new home aboard the Arkship, we unexpectedly crash-land in an uncharted region of space. The various devices carrying humanity’s knowledge and technologies are scattered across the wilderness, strewn beneath the light of a binary star.
This star system consists of a K-type red giant and a blue-white F-type main-sequence star. In orbit around the system’s eighth planet, the Arkship and its colossal ring-shaped space station, Huntian, separate during the crash. The Ring of Power breaks away and falls toward the surface of the moon, Lexing.
The eighth planet is an ice giant orbiting the binary stars. Its atmosphere appears red under the influence of tholin haze. The moon where the Ring of Power comes to rest is the primary setting of our game: Lexing.
Lexing is completely tidally locked to its parent planet, keeping the same face permanently turned toward it. As a result, the parent planet remains fixed in the sky, forever hanging above the same horizon.
In the distant past, Lexing was orbited by a small submoon. Its orbit eventually became unstable, and the submoon was torn apart by tidal forces. Its remnants spread outward, forming a faint, cold ring of ice and rock.
That is why, from the surface of Lexing, the sky is always adorned with two suns and a broad, luminous band of rings.
Now, you may be the last human alive.
Here, on Lexing, you will build a new home and carry the spark of humanity into the future.
Our goal is to rebuild and revive human civilization.
Using the remnants of the Ring of Power, you will begin at the most primitive stage of survival: living off the land, rediscovering fire, domesticating plants and animals, mastering steam power and new energy technologies, and eventually harnessing controlled nuclear fusion.
Then, you will ignite the artificial stellar engine aboard the ark mothership and begin the journey back Home.
When designing this world, we started from a simple principle:
Begin with what the players see.
Whenever we create an entirely new world, we want its fundamental rules to remain grounded in reality. Because only when a fictional world is constrained by the laws of real physics can it possess the sense of weight and credibility that makes it feel truly alive.
Today, let’s take a closer look at how we designed the binary star system.
The first point of reference in designing the system was the Hertzsprung–Russell diagram, or H–R diagram.
The H–R diagram is a scatter plot that shows the relationship between a star’s luminosity and temperature, first developed by Ejnar Hertzsprung and Henry Norris Russell. The horizontal axis represents surface temperature or spectral type, which determines the color a star appears to us. The vertical axis represents luminosity or absolute magnitude, which determines how bright a star is. A star’s luminosity also reflects the amount of radiation it emits, making it an important factor in analysing the location of the habitable zone.
One of the fundamental principles for reading an H–R diagram is simple:
Hotter to the left, cooler to the right; brighter above, dimmer below.
With this principle as our starting point, we selected and defined the two stars that make up our binary system.
We plotted the positions of the two stars on the H–R diagram:
Property
Primary Star A (Red Giant)
Primary Star B (Main-Sequence Star)
Spectral Type
K
F
Surface Temperature
~4,100 K
~6,300 K
Color
Orange-red
Blue-white
Evolutionary Stage
Shell Burning · Expansion
Core Hydrogen Fusion · Stable
Luminosity
High (Red Giant Region)
Moderately High (Upper Main Sequence)
Theoretical Model
Complex · High Degree of Freedom
Well-established · Well-constrained Parameters
At our current stage of stellar research, our understanding of main-sequence stars is far more comprehensive, while red giants still leave considerable room for further study.
The main reason is that main-sequence stars have relatively stable structures. Their core hydrogen fusion, internal structure, and underlying physical processes are comparatively well understood, allowing for mature and reliable theoretical models. Red giants, on the other hand, undergo shell burning, expansion, and mass loss. Their internal structures are considerably more complex, with significant mass loss making their dynamics and radiation processes much more difficult to model.
We deliberately chose a poorly constrained red giant and a well-constrained main-sequence star as the two components of our binary system.
The main-sequence star provides Lexing with a stable baseline of stellar radiation, giving us a reliable foundation for calculating its habitable zone. The red giant, meanwhile, leaves greater room for uncertainty in its parameters—creating additional space for both the narrative and the visual design of our world.
Once the basic properties of the two stars were established, we needed to calculate their various physical parameters with scientific rigor. Among the key theories we relied on were stellar evolution theory and Kepler’s laws of planetary motion, along with several others.
Stellar evolution theory is centered around nuclear fusion. It describes the complete evolutionary process of a star—from its formation and main-sequence stage to its expansion into a red giant later in life, and ultimately the end of its stellar life. It also explains how a star’s mass, temperature, and luminosity change throughout this process.
Kepler’s laws of planetary motion describe the fundamental rules governing orbital motion. They provide an important basis for determining key parameters such as stellar masses, orbital properties, and so on, making them essential to the quantitative calculation of the system’s fundamental parameters.
Only by taking these fundamental theories into account can we ensure that the design of our binary system holds up from a scientific perspective.
We are not going to present every calculation here—that would turn this into a paper on astrophysics. Instead, the core approach is straightforward: first, we use the H–R diagram to establish the luminosity and temperature ranges of the two stars; then, we use stellar evolution theory to constrain their plausible ranges of mass and radius; finally, we apply Kepler’s laws to derive the orbital parameters of the binary system and the distance to its habitable zone.
The binary star system has its greatest impact on the game in the way we designed its sky. In Lexing’s sky, a massive planet remains permanently visible, accompanied by fragments of its ring system drifting across the heavens. The design of this celestial landscape is primarily based on two physical concepts: tidal locking and the Roche limit.
Tides are a universal gravitational effect found throughout celestial systems. Tidal locking is a stable astronomical phenomenon that can emerge from the gravitational interaction between two celestial bodies. The tidal forces exerted by a larger body gradually alter the rotation of an orbiting body until its rotation period becomes synchronized with its orbital period. Once this state is reached, the satellite always keeps the same face pointed toward its parent body, while the opposite side remains permanently turned away.
In the game, Lexing is tidally locked to its parent ice giant. This means that, from the hemisphere where the player lives, the parent planet remains permanently fixed in the night sky—it never rises and never sets.
This is one of the most fundamental astronomical features of Lexing’s world.
The parent planet hangs at a fixed position in the sky, while its presence combines with the illumination of the binary stars to create a unique rhythm of day and night. Together, these elements form one of the most distinctive visual characteristics of Lexing’s sky.
Lexing is tidally locked to its parent ice giant while simultaneously residing within a binary star system. The combined gravitational influence of the parent planet and the two stars produces cumulative tidal forces, continuously pulling on the surface oceans and creating persistent tidal bulges.、
With an orbital eccentricity of 0.241, the tidal forces experienced by Lexing vary significantly as its distance from the bodies it orbits changes throughout its orbit. As a result, the magnitude of the tides rises and falls periodically.
Regular tidal cycles and recurring high tides occur in everyday conditions. The effects of ring-system shading and periodic gravitational perturbations from the two stars can also generate towering waves and storm-driven tides across the oceans. On top of this, the occasional impact of the rock and ice fragments can strike the ocean surface, triggering sudden surges and rogue waves.
These layers of tidal effects are reflected in different patterns of ocean behavior within the game. The table below brings together all the factors that influence Lexing’s tidal system:
Tidal Influence
Source Body / Factor
Effect
Primary Tidal Force
Parent Ice Giant
Persistent Tidal Bulge · Permanent Deformation
Secondary Perturbation 1
K-type Red Giant
Periodic Gravitational Fluctuations
Secondary Perturbation 2
F-type Main-Sequence Star
Periodic Gravitational Fluctuations
Orbital Eccentricity
0.241
Periodic Variation in Tidal Amplitude
Ring-System Shading
Ice and Rock Debris
Uneven Illumination · Ocean Temperature Fluctuations
Impact Events
Falling Rocks and Ice
Sudden Ocean Surges
“Do you miss the Moon?”
“Then you need a moon— one that was once a comet.”
Earth and the Moon are also a classic example of tidal locking. In the game, there is a celestial body that plays a role similar to our Moon. But in reality, it was once an extinct comet.
It began as an icy comet. After repeatedly passing close to stars, intense heat gradually stripped away the water ice and dry ice from its surface, leaving behind only a rocky, dusty nucleus. Eventually, it became completely inactive, no longer glowing or releasing jets of gas and dust.
In the game, the comet approaches from ahead of the planet along its direction of orbital motion. As it passes the planet, a gravitational slingshot bends its trajectory and significantly reduces its velocity, creating the conditions necessary for Lexing to capture it later in the game.
This “comet that once was” takes on the visual role of a moon. It no longer erupts, and it no longer carries a cometary tail. Its surface is nothing more than an exposed rocky, dusty nucleus.
But narratively, its history adds another layer of desolate poetry to Lexing’s night sky: this “moon” was once an icy wanderer, trailing a long tail across the stars.
When a celestial body passes within the Roche limit, the powerful tidal forces exerted by the primary body can overcome the object’s own self-gravity, gradually tearing it apart. The resulting debris can spread along the object’s orbit and, under the right conditions, form a ring system.
In the distant past, Lexing was orbited by a small submoon. As its orbit became unstable, it gradually spiraled inward and crossed within the Roche limit of its parent planet. The tidal forces eventually overwhelmed the submoon’s self-gravity, tearing it apart piece by piece.
The resulting fragments of ice and rock spread along its orbital path, eventually forming the ring that can still be seen across Lexing’s sky today.
Large fireballs can break apart and explode high in the atmosphere, creating a spectacular display. Most of the resulting debris burns up before reaching the ground, while larger fragments survive their passage through the atmosphere and fall as meteorites.
Fireballs are relatively rare, but their visual impact is extraordinary. Beyond their spectacular appearance, they are also valuable astronomical phenomena, providing scientists with opportunities to study the interaction between interplanetary material and planetary atmospheres.
In the game, when the comet is captured by the gravitational field of the ice giant, its passage disturbs the surrounding ring system. Fragments of ice and rock are knocked out of the ring and begin falling into the atmosphere, triggering a “fireball storm” that continues for several weeks.
The meteorites that fall to Lexing bring unique mineral resources from the ring system to the planet’s surface. Towering fireballs streak across the sky and strike the ground—both a danger and an opportunity.
Looking back at the worldbuilding of our binary star system, we have always followed one core principle:
Begin with the game’s visuals, while ensuring that the underlying setting remains grounded in real-world physics.
Every astronomical concept is more than a piece of lore added for its own sake. Together, they shape every frame of Lexing’s sky.
The timeline below brings together all of these scientific concepts and connects them to their corresponding visual elements and gameplay mechanics:
Step
Scientific Basis
Game Visuals / Mechanics
1
H–R Diagram → Binary Star Colors & Luminosity
Orange-red + blue-white dual-tone sky and lighting
2
Stellar Evolution Theory → Red Giant Instability
Shell burning & mass loss → Instability and suspense in the story
3
Kepler’s Laws → Orbital Eccentricity of 0.241
Changes in orbital distance → Periodic variation in tidal amplitude
4
Tidal Locking → Parent Planet Permanently Fixed in the Sky
The sky’s most distinctive permanent landmark
5
Combined Tidal Forces → Ocean Dynamics
Regular high tides + storm tides + sudden ocean surges
6
Gravitational Slingshot → Capture of the Extinct Comet
The “comet that once was” becomes Lexing’s moon
7
Roche Limit → Submoon Disruption and Ring Formation
A permanent band of icy and rocky debris across the sky
8
Fireball Storm → Major Narrative Event
A weeks-long fireball storm—both a nat
From plotting the positions of the two stars on the H–R diagram, to tidal locking that keeps the parent planet permanently fixed in the sky; from the Roche limit tearing apart the submoon and forming a ring, to a gravitational slingshot capturing an extinct comet, and finally to the arrival of the fireball storm over Lexing—every step is started from scientific theory, and every layer of worldbuilding ultimately serves the world the player sees.
This is the sky of Lexing:
Two stars. One ring. One vast red planet forever suspended in the sky. And a former comet serving as its moon.
Beneath this sky, the last human will light the spark of civilization once again.