The 3 Key Questions of Core Engine Design

We are back with a deep dive into Collectible Game Core Engine Design. For an overview of collectible game design, click here.

Core Engine Design is the starting point for building collectible games, and it can be intimidating to try and build a system with so many moving parts. Don’t let the open ended nature of this phase intimidate you! Your goal  is to answer a few key questions to help give shape to your game. You will have plenty of time later to work out details and refine your concept. Stay focused on these big picture questions to get your core engine running.


1. What is the Core Play Loop?

game loop


A core play loop is the basic pattern of play at the heart of your game. The core game loop should almost always be describable in a sentence or two. In Go, the core game loop is placing stones one at a time and trying to capture territory. In Call of Duty, the core game loop is Getting Weapons/Ammo, looking for enemies, and killing enemies before they kill you.

You will need to have other elements defined to properly test the core game loop (e.g. how does a player move, what are the damage ranges of various weapons, how high can my character jump, etc.) but these elements should be loosely defined and flexible. The goal is for all the peripheral rules and elements to be only “good enough” to test the core loop. You will have time to improve all the peripherals later.

There will be many broken things about your game in this phase. Strategies are not balanced, pieces are ugly, and many fundamental elements are still in motion. A designer has to see through all of that and see if there is a diamond of fun in the rough prototype. Training your instincts to find the fun and ignore the rough patches in early testing is critical.

While working on our digital collectible game Solforge, we had to do all of our initial prototyping on paper while still trying to design a game that worked best in digital. This required a lot of ugly “hacks” to make the game work. A single playtest game could take well over an hour! After that, we would usually change many things which could take several more hours to update and set up. After going through several failed systems including some that included terrain, fog of war, NPC monsters, and more, we settled on the basic core loop of cards that level up as you play them.

When you have a basic core play loop that is fun, you are ready to move on to the next phase.

2. What is the Fundamental Tension of the Game?


Your job as a game designer is to frustrate your players. Every game gives players a goal and then puts roadblocks in their way. Your goal in chess, for example, is to capture the opponent’s king, but the game wouldn’t be any fun if you could just reach across the table and grab it! 1

The design of good games puts restrictions on how you are allowed to act to make the goal challenging to reach. The “fun” of play is the process of navigating through obstacles to move towards your objective. You need to be conscious of what the tensions are, as this is what your game is really “about.”

In the tile-laying game Carcassone, players alternate placing tiles and “Meeples” to claim territory and score points for finishing roads, castles, and other structures. The tension of the game comes from having access to only one tile each turn. Finding the right tile to finish your structures while tactically using tile placement to protect yourself or make things more difficult for your opponents is the heart of the game.

In Solforge, the fundamental tension is around the core leveling system. Since each card levels when you play it, you need to consider both the current effect and the future impact of the leveled card. Players must decide whether to play cards that are good right now but don’t level as well vs. cards that are weaker now but are strong in the late game. This decision then in turn informs the opponent’s decision about which cards to play.

Almost all games have multiple layers of tension, not just one. For example, Carcassone has a limited number of Meeples you can use to claim territory, so deciding when to use and when to hold back Meeples is a key tension. Solforge also has lane based combat, creating a tension of whether to place your creatures defensively to stop opposing creatures or offensively in empty lanes.

It is valuable to identify all the tensions in your game, but it is most important to identify the fundamental tension. Whenever making decisions about your game, always ask “Does this reinforce or weaken the fundamental tension of this game?” If a new mechanic, component, a feature removes focus from the fundamental tension of the game, you should think twice about adding it.

There are many hard to answer questions throughout the process of game design. Identifying the fundamental tension early in the process will help guide you in answering those questions.

3. What are the Resources, Victory Conditions, and Axes of Interaction?

game resources
Every game design has to answer the following questions

  • What resources does the player have access to? (e.g. cards, gold, action points, one play per turn)
  • How does the player win the game? (e.g. eliminate other players, score X points, score the most points when time runs out)
  • How does the player interact with other players and the environment? (e.g. vying to control the same territory, Attacking a fundamental resource, racing on the same track)

Your core design isn’t finished until each of these questions has an answer. At this stage, the goal is to focus on how your game rules manage these systems- not how your individual components handle it. For example, having cards in your card game that specifically reference new victory conditions (e.g. you win the game if your opponent gets 10 or more poison counters) player interactions (e.g. Destroy an enemy tower) or new resources (e.g. Gain an insight token whenever you acquire this card) doesn’t count.

In collectible games, you can always add new rules with new components. You can’t, however, rely on those components to provide the gameplay you want because you can’t always guarantee what components will be present in each game.

There are countless possible variations of resources, victory conditions, and axes of interaction.  To help make things more concrete, in the next article I’ll go through a few basic examples and talk about the implications of each.


Putting it all Together


Core Engine Design is when you first take your inspiration and turn it into something that can actually be prototyped.  Finding answers to the inevitable questions that come up during design isn’t going to be easy, but  you can’t get the right answers until you ask the right questions. Use the questions above to help focus and bring your vision to life.

Want to know more about the building blocks of a game engine?  Click here.

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