How do users purchase objects in game? Unsurprisingly, there are a number of alternatives available to us.
Instant vs Build: Should purchases happen instantly, when at the click of a button the item springs up out of nowhere? Or a blueprint option, where the user places a “ghost” of an item and an in-game character acquires it from a depot and places it without user intervention?
Resources vs Money: Do I want to use resources such as wood and stone as currency, or something more abstract, like dollars? Should it be a combination of both?
Age of Empires II’s bankable resources
Bank vs Vault: Should the chosen currency be portrayed in the overlay, or should it be represented in the world as an interactive entity?
Buffet vs Unlocks: Do I give the user access to all purchasable items from the get-go, or should users unlock items throughout the game?
Replaceable vs Artifacts: Should all items be purchasable, or should the world contain unique, irreplaceable artifacts that can be fought for and lost?
The feature I think would be most fun is an in-game Vault. A place to store your precious loot and guard against would-be thieves. The concept opens up several possibilities. Items can be acquired and protected. Characters can guard entrances and patrol surrounding areas. Allies can betray you and swipe some coin when you’re not looking: sticky-fingered rogues! Traps (magical and mundane) can be set to capture intruders when your guards fail you.
Evil Genius’ vault full of gold bars, which are often stolen by both enemies and allies
If we assume the Vault is the way to go, then the other choices should support that feature. Items need to be a real thing: no instant-placements. If we want piles of gold, we need a use for it: items are purchased with gold rather than stone or wood. Gold exists as physical items, but the total amount needs to be displayed on the menu. The question of buffet versus unlocks is irrelevant for this feature, so let’s go with the easier option: everything purchasable is available from the start. To create a sense of real gain and loss, not everything can be bought: some items are unique and irreplaceable.
Dwarf Fortress has no currency. While everything has a value, players barter for items and resources they want with merchants at the trade depot.
Now I just need to implement everything. Easy, right?