Mars Crisis: The story engine

This post is the first in a series of three posts where I go into the details of the Mars Crisis story engine. Mars Crisis is a one man project, started August 24th. It’s based on Twine 2 using the Harlowe 3.2.2 story format. The latest version of the game is available here.

The story engine is what supports the game generating a story that addresses the theme. The theme is why we play, the question (or questions) we try to answer with the story we create through play. In Mars Crisis, we play to find out if Kelly saves the colony and at what cost (how she is remembered). 

When you play Mars Crisis, you don’t see the story engine. It’s hidden under the hood. I want the players to immerse in the flow of the fiction, not engage with the numbers. However, when you engage with the fiction at crucial times, the story engine kicks in and pushes the story in specific directions.

Story engine = state + transitions

The story engine consists of a game state and of state transitions, also called moves. The game state in Mars Crisis is how Kelly and the colony is doing right now. The moves are how Kelly can influence someone to support an initiative. In a classical rpgs, think of game state as hit points and experience points. The moves are the actions players can take during encounters and where characters can loose hit points and earn experience points. In chess, the game state is the position of the pieces and the moves are the legal moves that the players can make.

The game state can only change through moves. Moves are when the fiction connects with the story engine and the the game state changes. 

State of the colony

So let’s build a story engine for Mars Crisis with a game state and transition rules.

To save the colony, Kelly must make progress resolving threats to the colony. Let’s boil it down to three fronts and put some numbers on it to track the progress:

  • Economy. Can the colony generate an income that allows it to be independent of funding from Earth?
  • Infrastructure. Can the colony provides a healthy and safe environment where colonists want to live?
  • Crime. Do the laws of the colony reflect the needs of the people and do people follow the laws?

For example, Strike at Mars Drilling threatens the Economy of the colony. There are callouts to Crime with the theft of property and to Infrastructure with the work safety hinted at in the background to the strike, foreshadowing other issues to deal with.

Let’s have each start at 0 and each time Kelly overcomes a challenge, advance it by +1. Let’s not decide on the maximum possible values yet, that depends on how much content ends up making it into the game.

The state of the colony as it is defined in the editor.

State of Kelly

To represent the cost that Kelly can pay, let’s give her some resources that she can spend and perhaps replenish. In a classic RPG game, these would be health or hit points. In Mars Crisis, we track:

  • Integrity. Integrity is about staying true to your ideals and keeping your commitments. The occasional lie or unfulfilled promise can win opponents over here and now but on the long run, Kelly may lose sight of why she is here and people will stop trusting her.
  • Popularity. How well Kelly is perceived in the colony. Necessary but unpopular changes can take its toil on any leader who wishes to remain in office.
  • Reserves. Spending money here and now to sweeten a deal is definitely on the table of most political discussions. Money can solve some problems, while the supply of money is never endless. So let’s give Kelly a budget for Kelly to sweeten the occasional deal. As reserves run low, we can trigger new stories with Kelly being called in front of the budget committee to defend her spending decisions. 

When she “takes damage”, these are the resources she lose. For instance, making a promise that she can’t keep to win someone over damages her Integrity. Imposing a necessary but unpopular change can make her popularity drop. Let’s start each at 3 and put an end game criteria in that if any one of these drop to 0, Kelly looses her ability to improve the colony. Maybe she is kicked out of office when her popularity drops to 0. 

The state of Kelly at the start of the game as it is defined in the editor.

In addition let’s keep track of time and have Kelly’s term expire after a certain amount of moves. There is always more to do and putting an opportunity cost of addressing one issue while neglecting another feels right for a politics game. It also means we can have crises and events appear as time pass.


Hence, the game state boils down to:

  • $Turn
  • $Economy
  • $Infrastructure
  • $Crime
  • $Integrity
  • $Popularity
  • $Reserves

The next post will go into the moves of Mars Crisis.

In the mean time, enjoy a game of Mars Crisis.

Kelly's notes on herself updates to reflect her current Integrity and Popularity scores.