Previously, I described how the cards in Mabeopsa suffered from the elemental damage problem where the cards are similar but with different elemental names (e.g., fireball, ice bolt, acid splash, …). Overcoming this issue required identifying the resources and the spaces available that could differentiate the five elements. Let me describe the process I took using the fire element as an example.
Like many card games, Mabeopsa has the concept of a deck, a hand, and a discard pile, adding health, energy, and the current range. Cards have an element, an aspect, playable range, speed, and energy cost to play. Cards may have a persistent effect as well.
Originally, I had pictured fire cards as being somewhat analogous to black cards in Magic: The Gathering with an emphasis on burning resources to get ahead, discarding a card or sacrificing health to do more damage. Initial playtesting suggested that it wasn't worth sacrificing health to do damage as player health is very small compared to Magic (6 vs. 20 starting health at the time) and because health persisted between rounds.
So I changed fire cards to focus on discarding. Thematically, this still worked to suggest burning cards for energy and also suggested lowering the energy costs on many of the cards. It also required looking at how discarding would work. Players select a card to discard in most games, and initially I thought that Mabeopsa should ask players to do the same. Just as I started implementing the feature to do so, though, I realized that the player's hand could be treated spatially to make discarding more interesting.
Consider a fireball spell. Fireball is a standard area-of-effect high damage spell in many games. Without friendly damage, there's little reason not to use it unless opponents are immune to fire or some such. Adding friendly damage makes fireball interesting and conditional. In Mabeopsa, I tried to emulate this by making discarding always take the bottom-most card. This will be the most recently drawn card unless the player selected their bottom-most card to play, which places a bit more emphasis on the previously-held cards. This decision also suggested cards that changed the position of the cards in one's hand, further diversifying fire from just being about damage.
The other elements fell into place with their own specializations: The deck and drawing cards, using the discard pile, and manipulating status effects. The hardest was metal, which specialized in ranges, and that decision also forced another pass through the cards.