Sublight Empire Overview


Einstein's theory of relativity states that nothing is faster than light. This also applies to this game.
Information is radio signals propagating at the speed of light (denoted as c). These radio signals transmit your commands and the events you receive.
Starships move at a fraction of c. So it takes years for a command or a starship to reach its destination. When a battle takes place, you won't know about it until years later.

Apart from this, it is a classic 4X game.
In the beginning you rule a single star system and you are exploring and colonizing the surrounding systems.
Later on you will meet your opponents and you will have to defend and conquer colonies.

The game is completely fair, your AI opponents don't get any advantages or information you wouldn't get in their place.

Your role in the game

You are the emperor and you are on your throne ship, which you can move to any of your colonies.
From there you send orders to your star systems.

Since you are a part of the game world, you are bound to the physical laws of this world, such as the speed of light.

You deal exclusively with interstellar affairs, you don't bother with internal affairs of your colonies.

You have the monopoly on everything that has to do with interstellar spaceships. On your orders interstellar ships are built, launched and scrapped.
These are the only 3 orders you can give, so it's a very minimalistic gameplay.
But these 3 commands are very powerful, you can explore, colonize, conquer, trade, and so on.

To win the game, you must conquer 2/3 of all stars.

Star Systems

Colonized star systems are the foundation of your empire. They execute your commands. But they only do it when they in your debt.

Spectral type

Each star belongs to one of the following spectral types, sorted from hot to cold.

Type Color Count Max. Pop.
A Blue 1/15 3
F White 2/15 5
G Yellow 3/15 9
K Orange 4/15 5
M Red 5/15 3

The hotter spectral types are rarer, but generate new tech points faster than the cooler ones.

The maximum population does not mean, for example, that every yellow star can grow up to 9 billion inhabitants — it depends on the individual star how many inhabitants it can actually have.


Each star system grows after colonization until it has reached its maximum population.

One spaceship can be built or maintened for every 1 billion inhabitants. This means that battleships or trade ships that reach a system without free population are automatically disbanded.

Starship Speed

The more ships a system launches, the more tech points are generated and thus higher speeds are researched.


Instead of money, there is a debt system that is maintained with trade ships.
Your colonies are grateful to you or, in other words, are in your debt when you send them trade ships.
To repay or reduce this debt, they build and launch spaceships when you send orders.

A star system builds and launches spaceships only if it has enough debt to you. Debts of systems are increased or decreased if they belong to you:

  • Increase when the throne ship arrives
  • Increase after arrival of your trade ships
  • Increase after scrapping
  • Decrease when spacecraft is built
  • Decrease at spacecraft launch


Happy systems have many advantages. they do not rebel or go on strike, defend better against attackers and are more resistant to man-made disasters.

Ships from happy systems also have advantages:

  • Probes send longer
  • Colony ships found more happy colonies
  • Culture ships generate more happiness points
  • Trade ships generate more revenue
  • Tech ships generate more tech points
  • Battleships and invasion ships are stronger

You can increase the happiness by sending culture ships from systems with higher happiness to systems with lower happiness.

Disasters and wars makes your systems unhappy.


There are 8 types of ships.

Throne Ship

Imagine you're on this ship.
An event is visible to you when the signal reaches your throne ship.

You can move your throne ship to explored systems, but you can not build one.

Your colonies don't accept orders from you when you're in a enemy system.
The only order that can be given in such a situation is to launch the throne ship.
During the voyage of the throne ship, you are in cold sleep and cannot give orders.

If you move the throne ship to another system, the debt in that system is increased by 10 per moved light year.


Explore systems with probes.

Colony Ships

Colonize systems with colony ships.

Trade Ships

Increase the debt of colonies with trade ships.

Culture Ships

Increase the happiness of colonies with culture ships.

Tech Ships

Increase the technology level of colonies with tech ships.


Defend and conquer colonies with battleships.

Invasion Ships

Suppress Rebellions.