Slay Divinity is a roguelike deckbuilding game, which means players build a deck over the course of a run and use it to fight enemies in card battles.
The most common way to add cards to the deck in Slay Divinity is getting a card reward: A choice between three different cards, one of which is added to the deck.
The Card Reward Screen
My goal is to improve the balancing of the power level of the different cards. While the power level of a card in a run depends a lot on the context, some cards are more powerful more often than other cards.
Cards that are too powerful too often may become “autpicks”, reducing player choice and making runs more monotonous.
I’ll try to identify the most and least powerful cards and tweak them to make deckbuilding choices more interesting for the player.
Measuring the actual power level of a card is a complicated issue, which is why we’ll be using “popularity” of the card as a proxy. Luckily, popularity tells a more complete story than power alone, as we’ll see later.
We operationalize the popularity of cards by comparing how often they are picked (actual pick rate) with how often we would expect them to be picked based on their rarity (expected pick rate).
Actual Pick Rate > Expected Pick Rate ⇒ more popular card
Actual Pick Rate < Expected Pick Rate ⇒ less popular card
The Actual Pick Rate is simple enough to measure: The game tracks whenever a card is shown as a possible reward, and how often the card is picked.
Actual Pick Rate = Card Picked / Card Shown
All things being equal, you’d expect each card to be picked 1/3 = 33.3% of the time.