Externalities Make Games Easier to Learn

The biggest barrier to introducing a new game is teaching someone how to play. They not only need to learn the rules but also figure out which strategies and goals to pursue before understanding all the possibilities. People often react poorly to being told what strategy to follow. A better approach is to ensure every goal they complete creates new opportunities and threats, giving them a new hook to pursue when they wonder what to do next.

In economics, an externality is a cost or benefit borne by a third party to an activity, and we can borrow the same terminology here. Externalities are new threats or opportunities created while pursuing a goal. They emerge as unintended side effects of the player's actions and create new, meaningful goals beyond the player's original goal. Here are some examples of externalities in popular games:

• In Catan, you build a road to get to a location on the board and then realize that you are now only one road shy of the Longest Road bonus. The externality is the opportunity to claim the Longest Road. Your new goal is to build enough roads to secure it.
• In Slay the Spire, you add "Wild Strike" (Deal 12 damage, gain a wound card) to your deck because you need more damage. The externality is the threat posed by the wound cards you are accumulating. Your new goal is to find effects that can remove wounds or convert them into something useful.
• In Factorio, you successfully expand your factory but, in doing so, create a lot of pollution. The externality is the threat posed by the swarms of aliens drawn by the pollution. Your new goal is to build sustainable defenses.
• In Spirit Island, you played a power card because you needed its elements to meet an innate power threshold. The externality is the opportunity to take advantage of the text effect on the card you played. Your new goal is to find a use for that effect.
• In Spelunky 2, you successfully robbed a shopkeeper to gain useful items. The externality is the threat of the Shopkeeper's Association, which is after you now. Your new goal is to avoid drawing any more heat from them until you are forgiven.

Externalities benefit new players by reducing the burden of choosing strategies. Once they start playing, they naturally encounter new goals to pursue. Pursuing those goals creates even more goals, leading to a loop of goal creation that allows them to focus on "how" rather than "what."

By guiding new players through the rules one subgame at a time, externalities help them learn more easily by exposing rules as they become relevant to their goals. Each opportunity or threat interacts with a different part of the game, guiding players on a gradual tour of the mechanics with immediate relevance. People find it easier to understand a system when it feels immediately relevant, which is why rule explanations often start with a game's goals.

As players learn more about the game, they may start to understand when to go against the natural flow created by externalities. Veteran players no longer need externalities to guide gameplay because they have automated much of their thought process and internalized the mechanics. But guidance still reduces decision fatigue and continues to help even after they clear the initial barrier to entry.

Using externalities in your games requires only that you examine the goals your players face and ask yourself for each one, "What actions do players take to achieve this goal? What other opportunities or threats do those actions create?" If the answer is none, then you know what to try next

New players need guidance, and you can't always count on experienced players to have the right approach. By building externalities into your game, you create a network of branching paths for them to explore in whichever order they choose.