Heliosyn

What if a 4X space game made no compromises? No feature cut for being “too complex to code.” No physics simplified for being “too hard to balance.” No AI dumbed down for being “too expensive to build.”

Heliosyn is a hard-SF grand strategy game in the spirit of Aurora 4X, High Frontier and EVE Online, but free to go wherever the simulation demands. 1,000 real stars. Atmospheres that obey physics. Rival empires that plan wars and adapt their strategy over centuries. Every mechanic, from genetic engineering to fuel logistics, runs on simulation, not abstraction. A campaign spans 1,500 years of galactic history, and nothing stops you from playing well beyond.

About development: Heliosyn is designed, specified and tested by a solo developer, with the code written by an agentic AI assistant. Every mechanic is human-designed and human-validated. The AI is the engineer that makes a simulation of this scale possible for one person. In-game AI (rival strategists, the ARIA assistant) runs on a local model on your own machine: no cloud, no account, no data sent anywhere.

✅ What’s already in place

Universe & exploration

• 1,000+ real stars from an astronomical catalogue (HYG): positions, spectral types, binary systems.
• Procedural systems (planets, moons, asteroids, comets), each with its own physical properties, plus jump points based on real celestial coordinates.
• Galactic map with seamless zoom into the system view, fog of war, and corridors visible only toward visited systems.
• Discovery system: bodies are detected before being scanned. An unknown body shows only an anomaly and “???”.

Physics of celestial bodies

• Atmospheres modelled in partial pressures: each gas tracked independently, with greenhouse effect, composition and O₂ ignition.
• 20 emergent climate phenomena (water cycle, cryosphere, weather, magnetosphere, biosphere, geology…) with long-term effects on the atmosphere.
• Gravity, temperature (radiative equilibrium plus atmosphere) and a composite habitability score, all computed from each body’s properties.
• Resources on every body (gases, metals, heavy isotopes, organics), weighted by body type.
• Playable terraforming: a long, delicate, irreversible process. The climate cascade reacts to every action, and atmospheric physics does not forgive.
• Atmospheric catastrophes (11 live): solar storms, supervolcanoes, runaway greenhouse, ozone depletion, atmospheric ignition…

Interface

• EVE Online-inspired tabular tactical view (Overview) with filters, sorting and context menus.
• Dedicated panels for empire, wealth & economy (persistent HUD), terraforming and genetic manipulation.
• Visual doctrine designer (behaviour-tree editor with built-in tester) and a visual tech tree of 800+ entries across 15 categories.
• In-game manual, filterable event log recording every battle, discovery and construction.

Fleets & doctrines

• Fleets with order queues: move, orbit, patrol, explore, refuel, transport, all issued directly from the map.
• Doctrine system based on behaviour trees: define how fleets react without micromanaging (patrol, tactical retreat, target priority, auto-refuel, return-to-base on fatigue). Presets included and fully editable.
• Complete fuel logistics: smart auto-refuel (stockpile or ship-to-ship), fuel guard, unloading to planetary stocks.
• Gas Harvesters (He-3 on gas giants), orbital mining of asteroids, and multi-fleet space-station construction.
• Crew endurance & maintenance: fleets that stay out too long degrade and head home.

Combat & warfare

• Full combat with 13 weapon families (beam, kinetic, missile), shields, multi-layered armour and damage control.
• Missiles as real objects: salvos fly through space in continuous time, home on targets, run out of fuel and get intercepted, with Aurora-style mid-course and terminal guidance.
• Special warheads (nuclear, antimatter, EMP, decoys) and dormant minefields that ambush intruders.
• Per-module damage: a ship with a dead reactor goes dark but can still run; reactors, fire controls and weapons take damage separately.
• EMCON: engines and sensors give your position away, so play with radio silence or fully assume your presence. Power must be budgeted at design time; no free energy.

Ships

• Modular design: assemble ships from modules, themselves built from technological components.
• Specialised systems (refuelling, gas harvester, fire control, tracking mounts, layered armour) with DPS-by-range and armour charts, so ships behave the way you built them.
• In-place refit: upgrade existing ships to a newer generation instead of scrapping them.

Colonies & economy

• Earth as starting colony; 16 building types (mines, factories, labs, shipyards, terraformers, genetic centres, refineries…) with real resource and time costs.
• Full imperial Wealth economy and per-body stockpiles produced tick-by-tick, routed between bodies by mass drivers.
• Research queue across 15 categories; realistic population growth driven by habitability and living conditions.
• Working genetic manipulation: 63 modifiers across 4 tolerance axes, but overreach triggers instability and extinction. Every subspecies is a long-term bet.
• Personnel: officers with ranks and ages, naval academies, crew bonuses.

AI rival empires

• Rivals play by the same rules as you: they explore, colonize, mine, research, design their own ships and missiles, and pay for all of it with the same economy. No cheating, no free units.
• Differentiated archetypes (militarist, merchant, expansionist, paranoid), each weighting its priorities.
• Real war conduct: intelligence, fleet staging, strike, battle-damage assessment, exploitation or withdrawal. Wars end when the objective is reached.
• A local LLM as war strategist reviews each empire’s situation and issues directives, differentiated by personality, running on your machine.

ARIA, your onboard assistant

• An LLM assistant built into the game, fine-tuned on Heliosyn’s mechanics and running locally: no cloud, no account.
• Ask how terraforming, EMCON, ship design or genetics work, in plain language, without leaving the game.

🔭 What’s coming next

Short term

• Bug fixing
• Onboarding (tutorials, tooltips, ARIA-guided first hours).
• Implementation of end game objectives and Ground combat.

Medium term

• More catastrophe categories (geological, stellar, biological, social; ~26 additional events specced).
• Balancing pass driven by long AI-vs-AI campaigns (weapons, tech pacing, economy).
• Governors and deeper personnel careers.
• Implementation of various threats and more event to push exploration.
• New 2.5D rendering engine
• New UI

Long term

• Diplomacy beyond war and peace (treaties, trade, coalitions).
  
• Mod support surfaced to players (data and script mods)

💬 Join the community on Discord to share feedback, report bugs and follow development.