The following is an excerpt from the Designer Notes for Offworld Trading Company. The game, an economic RTS set on Mars, releases on April 28, 2016, and is available for purchase here.

A game with 13 resources would not be very interesting if all 13 resources are basically different flavors of the same thing. Thus, when building the resource tree, we had to think about what purpose each resource served. The natural place to start is the primary resources which are found on Mars. We decided early on to have five primary resources which would appear randomly on the map (although also depending on terrain so that, for example, Iron is most likely to be found on Volcanic terrain). The initial five resources were Water, Iron, Copper, Aluminum, and Silicon. Our secondary resources would derive from the primary ones, creating a resource tree similar to those found in the Railroad Tycoon series:

• Greenhouse Farms turned Water in Food
• Electrolysis Reactors split Water into Oxygen and Fuel (Hydrogen)
• Plastics Manufactures turned Fuel into Plastics
• Steel Mills turned Iron into Steel
• Glass Kilns turned Silicon and Oxygen into Glass
• Electronics Factories turned Silicon and Copper into Electronics

This resource tree meant that certain resources were easier or harder to obtain. Steel was easy to make as it simply required Iron while Glass was much hard as it required Silicon and Oxygen (and the latter comes from Water). This difference kept the market interesting as players had to judge a resource not just by its price but also by how hard it was to make the resources. If Glass is $100, and Steel is $80, it’s not immediately obvious which resource is better to produce as Glass is harder to make and also sensitive to price changes in three different resources (Silicon, Water, and Oxygen).

Furthermore, the resources were differentiated by how they were to be used. Steel was the primary construction material, used to create almost all of the buildings and also to upgrade the HQ, which makes it a very important resource early in the game. Copper and Glass were also used to upgrade the HQ, which made them similarly crucial as upgrading was the primary method to acquire new claims. Other resources – Water, Food, and Oxygen – were needed as life support to keep one’s workers alive. These resources were consumed every turn depending on the size of the HQ, which meant that their price would rise steadily if no one was supplying them to the market. Similarly, Fuel powered the player’s ships as they moved across the map. Aluminum was used for building ships at the HQ (which was important in this earlier version of the game). Plastics and Electronics (as well as Glass) were cash crops that were not particularly useful to the player but could be driven up in value by onworld demand (a background factor that replaced the old neutral Colonies). A final resource, Power, worked completely differently from all the other resources because it could not be stockpiled and was constantly bought from or sold to the market depending on whether the player had a shortage or surplus of it. Power was important because almost every building in the game consumed Power while working, which meant the demand for Power would consistently increase until players ran out of claims for new buildings.

Thus, every resource in the game had a unique profile regarding how it was made and why it might become valuable. This diversity meant that players knew that investing in a specific resources meant different things for their overall strategy – claiming Water was important for ensuring access to life support, building Glass ensured that the player could upgrade and claim more territory, making Electronics meant that the player would be able to make cash by selling a rare and expensive resource, and so on.

Of course, the resource tree changed a few times before our final version. One concern was Aluminum, which wasn’t a particularly interesting resource as it didn’t lead to any secondary resources. Furthermore, we liked that the Metal Mine could sometimes produce multiple resources if the player found a tile with multiple deposits of Iron, Copper, and Aluminum, and we wanted the same feature for the Quarry. However, instead of cutting Aluminum, we cut Copper and moved Aluminum into its slot as an upgrade resource for the HQ. (By now, ships were no longer constructed by the player, so we also didn’t need a resource dedicated to that purpose.) To take the place of Copper, we added Carbon, which would also come from the Quarry so that it could ideally produce multiple resources (Silicon and Carbon). Electronics would now also come from Silicon, Carbon, and Aluminum, making it unique as the only resource that required three inputs.

The final change to the resource tree was to replace Plastics with a more interesting resource. Electronics and Glass were useful cash crops based on onworld demand, but they were also important for either building the Offworld Market or (in the case of Glass) upgrading the player’s HQ. Plastics, on the other hand, really didn’t have a purpose if the price was not high. At the same time, we had learned that the game was more interesting if costs were in resources, not in cash, so that their true price fluctuated depending on the market. Patents and optimizations had been priced simply in cash, but if they cost a resource instead, players could decide to make that resource to help themselves conduct research (or to profit from other players’ research). Thus, we replaced Plastics with Chemicals, which would now be used for patents and optimizations. Further, Chemicals would come from Fuel and Carbon, making the resource similarly difficult to make as Glass and Electronics.