Using Cost Curves to Balance Card Costs

In Monster Zoo, I try to keep cards balanced according to their cost to acquire. Cards with stronger effects typically have higher costs and weaker cards have lower costs. However, after a few rounds of play testing Monster Zoo, I realized that some cards in the game were out of balance. A few cards felt really strong and could easily sway the game towards a player’s favor quickly. And a few cards seemed really weak, when played they had little effect on the game or felt too expensive to acquire.

One of the best discussions I could find on the topic of balance is a lecture from Ian Schreiber on Transitive Mechanics and Cost Curves. In the lecture, Ian talks about breaking down all the individual effects of your game into two things: costs and benefits. By doing this, you can get a sense of how balanced all the components of your game are relative to each other. If a particular item has a much higher benefit to cost ratio than other similarly costing items, then you know something is out of balance.

Here’s how I went about applying this principle for Monster Zoo.

First I broke out every single card into it’s individual effects. For example, the card Whompo Boogly has the following stats: “+2 Food. Zoo Effect: Draw an extra Card this turn.” This card has two unique effects:

  • Food Gained
  • Zoo Effect that Draws Cards

After identifying every effect, I then gave a rough benefit score to each effect in relation to other effects. Then I added up the value of every benefit per card, giving me a benefit total score.


Now I have a rough cost / benefit comparison for each card. But it’s hard to really get an idea of where some of the cards might be unbalanced.

This is where a cost curve (basically a visual representation of your cost / benefit) comes in handy. Charting out the cost / benefit of all the cards gives me this:

cost curve


With this, I can see that there are a few cards that are unbalanced in a few ways:

  • There are cards with a cost of 3 that have less benefit than some cards with cost of 2. (Underpowered)
  • There are cards with a cost of 5 that have less benefit than some cards with cost of 4. (Underpowered)
  • There are cards with a cost of 4 that have more benefit than some cards with cost of 5 or 6. (Overpowered)
  • There are cards with a cost of 6 that have much higher benefit than the natural cost curve. (Possibly Overpowered)

Let’s look at two specific examples.

One of the cards that seemed overpowered in play testing was Fifi Oogly. This card has the following stats:

  • Cost: 6
  • Benefit: 9
  • Gain +2 Food
  • Monsters cost 1 less Food to catch this turn.
  • Zoo Effect: Monsters cost 1 less Food to catch this turn.

Based on the cost curve, you can see that this card has much more benefit than it’s cost. So we have two options here, we can increase the cost or we can reduce the benefit. I happen to think it’s a fun card to play with, so I’ll likely test increasing the cost.

Here’s another card, Yummli Oogly. In play testing, this card seemed weak and no one really wanted to acquire this card. Here are the stats:

  • Cost: 6
  • Benefit: 5
  • Double all Food gained this turn.

While this card seems like a really strong card, it definitely is below the curve. If you compare it to a card like Chunky Oogly which has the following stats:

  • Cost: 3
  • Benefit: 4
  • Gain +2 Food
  • Draw an extra card this turn

You can see how Yummli Oogly is fairly weak, on the cost curve it is seriously below everything else with a cost of 6. Having 2 Chunky Ooglies would be much better for the same cost. In this case, I might add an effect to Yummli Oogly to get it back in balance.

Some guidelines for creating your own cost curve and using it to balance your game:

  • Break down all effects into individual unique effects
  • Assign a relative benefit value for each effect
  • Create one cost value for each item
  • Compare the cost / benefit to understand balance

One thought on “Using Cost Curves to Balance Card Costs

  1. Pingback: Excel and Google Docs Spreadsheet Tips for Game Designers #2 | Ruby Cow Games

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