Double-Spending Improves Texture

There are many types of resource costs in games. Some permanently sacrifice a resource; others only temporarily exhaust it. Some only require reaching a threshold without spending anything. Multiple cost types in one game add texture by letting a player spend the same resource in two ways. This is double-spending, and it is a great way to make players feel clever.

One common source of double spending is having both "exhaust" and "sacrifice" costs. In Oath, some actions flip secrets face-down, while others permanently sacrifice them. However, you can sacrifice a face-down secret, effectively using it twice. If you are going to burn a secret anyway, why not get some extra use out of it first?

I use sacrifice costs in my game Sprocketforge. You have a factory of gears, and on your turn you can produce to earn the rewards shown at the bottom of each gear. You can also disenchant a gear, producing with it but removing its production symbols. If you produce and disenchant on the same turn, you can trigger a production symbol twice. This is even more powerful for 2x production symbols. Double-spending at the right time can create a huge, satisfying turn.

Externalities also create opportunities for double spending when costs generate extra resources. In Inscryption, you play a card game where your creatures are resources. Weak creatures are free, but to play stronger ones, you must sacrifice others. Whenever an ally dies, whether in combat or through sacrifice, you earn bones. Some creatures cost bones to play. You can sacrifice a creature to summon a stronger one, then spend its bones to summon something else as well. The same sacrifice pays for two different things.

Sacrificing units as a cost also allows double spending in another way: health is a resource too. In AEGIS, players field a squad of five robots to fight their opponent's five robots. As an action, they can combine two or more robots into a more powerful one. When they do, they remove all damage and ongoing effects from their robots. Combining at the start is wasteful because the robots are at full health, but waiting risks one of them dying. Double-spending creates a push-your-luck dilemma of how much health to spend before combining.

Threshold costs create a different opportunity for double-spending: overlapping thresholds. In Spirit Island, many powers have stronger abilities unlocked by generating elements. Unlocking a threshold does not consume the elements, so you want to find powers with similar thresholds. Then you can efficiently unlock all thresholds at once with the same elements.

My card game Weavers was based mostly on overlapping thresholds. Players had spells with steps that needed to be completed in a specific order by generating symbols. A single symbol would pay for any number of different spells that required it that turn. The core puzzle was how to play your spells in the right order so their steps overlapped. This challenged players to juggle as many spells as possible at once.

Double-spending creates texture by letting a fixed effort yield many times the reward when you time purchases well. When designing resource costs, ask yourself: what ways can this resource be spent, and how do they overlap?