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.

Core Design Loop Step 2: Set Parameters

Once you have your Inspiration, you need to set parameters for your design.  One of the biggest challenges of designing a game is how open-ended the process can feel.  Especially at early stages, everything feels in flux and the limitless possibility can be very intimidating. To solve this problem, you need to set parameters.

Create More by Changing Less

Game systems are delicate creatures- changing one part can have ripple effects on the whole design, so it is helpful to define parameters that keep you focused.  Deciding to hold some things constant allows you to be most effective with the changes you do make.  Staring at a blank page with no limitations can be very daunting, but knowing that you want to make, for example, a $14.99 retail card game for 8-12 year olds, can immediately start you down a path.  Limitations breed creativity.

Be Your Own (Tough) Boss

One of the benefits of designing games for hire is that parameters are often set for you.  You will usually be told who your game is for, what the theme will be, and when the game needs to be complete.  These things (especially the deadline) do a wonderful job of focusing your attention on what really matters.  When you are just starting out or designing games on your own, you need to be your own boss and define these parameters for yourself.

Key Questions to Set Parameters

Here are some helpful questions that can guide you in this process.  Answer the below questions for your game and hold those answers constant through your first design cycle.  You can change them later if need be, but there is value in wrestling with the limitations you set for yourself before you relax them. 

1. Who is your target audience?

While we all would love to design games enjoyed by everyone, you need to pick a smaller target to aim at when designing your game.  What key attributes define members of your ideal player group? Try to think about their age, hobbies, interests, etc.  Create a mental picture in your mind of someone in this group. What activities do they engage in?  What motivates them?  What types of things do they buy?  What kind of games do they play now?  Why do they play those games?

Answering these questions and keeping a mental picture of your target audience in your head will help guide your design process.  Don’t try to make your audience too broad, especially at first.  It is a common mistake amongst designers to think their game is for everyone- if you are trying to design something for everyone, you are really not designing for anyone.  Keep your focus small- envision one member of your target audience and design a game for them specifically.

The easiest target audience to design for is yourself. Being able to create games that you yourself love to play has the wonderful advantage of it being obvious when you succeed or fail.  Even if you are targeting yourself, however, make sure that you find others who also fall within your target audience to playtest your game and provide feedback.  We are often blind to our own shortcomings and only the harsh reality of playtesters outside of your design team can truly give you the feedback you need.

2. What is your hook?

Every great game has a hook. Each year, hundreds of games are released and available online and on store shelves.  What makes yours stand out?  There are lots of possible answers to this question, and hopefully you have developed yours during the inspiration step, but its worth thinking out and writing down explicitly. 

There is a principle in business called the “elevator pitch”- imagine that you just so happen to be in an elevator with a wealthy game investor.  You only have a minute to convince this person that you are worth their time after the doors open.  How do you do this?  There are many approaches, but the easiest is to connect two exciting things in a unique way (e.g. Angry Birds with Star Wars characters, Digital Trading Card game plus Tactical RPG, Deckbuilding Game using Dice instead of cards, etc.).  

The same principle will apply with your customer as they browse past your game in a store or ad.  How would you describe your game in one or two sentences?  What differentiates it from other games?  Note that this doesn’t mean your whole game needs to be described in two sentences, just the unique hook that gets someone interested.  If answering this question takes more than two sentences, you need to refine further.

3. What restrictions do you have?

Every design process has to have some restrictions- some of them more severe than others.  Think about what you must work around and what will constrain your design.  Do you have a deadline? Do you have a brand or intellectual property you have to design for?  Do you have cost limitations? A programming language or platform you must use?  As counterintuitive as it is, even if you are designing for yourself and have no immediate restrictions of time and cost, it can be very helpful to artificially create these restrictions.  Remember, limitations breed creativity.  Placing deadlines on yourself 1 forces you to focus on what matters and helps you to rapidly move a game forward, rather than endlessly refining and tweaking and procrastinating.  Write down your restrictions and use them as guidance for the next phase- you can always come back and change them later.

Forging a Path

For my own design, Solforge, I knew I wanted to create a digital card game that was playable on PC, tablets, and phones.  Since I partnered with Richard Garfield, creator of Magic: The Gathering, the pitch was “Magic, for mobile, for free.” 

I wanted to take advantage of the cool things that could only be done in digital gaming, but I self-imposed a restriction to make mechanics that could still be tested with paper cards.  This was in many ways a paradoxical and challenging restriction to work under: Do things that only digital cards can do, but find a way to playtest them in physical-only format.  This forced our design team to come up with clever ideas that let us quickly prototype and iterate without all the expense of implementing a digital version before we were ready.  We came up with the primary mechanic of cards leveling as you played them, which was a big hit with our players. 

To test the game physically, we used “stacked” papers in a protective card sleeve, that could be changed out as the card was played to show that it had leveled up.  The playtesting process was painful (especially having to “reset” all the cards after the game). We knew that once we had something that was fun, even with all the pain of physical testing, that the game would be great once the digital took care of all the hard parts.  Once we took the idea to kickstarter and had backers, suddenly an enormous number of restrictions and deadlines pushed us forward.

Remember, parameters you create are not set in stone, but they are going to help you through the rest of your first design cycle.  The above example illustrates how holding some variables constant can help drive your creativity and move you quickly into the prototype phase.  Those creative leaps forward come during the next phase of the design cycle 2Brainstorming.   

This article has been updated and posted on steemit!