Game Economy 101

A game is a simplified economy. In Doom, you collect power by killing demons, which you can use to power weapons to kill more demons. etc... It can be looked in terms of:

• Taps: The generation of resources. Some taps generate resources on a timer (health) others have to be harvested by the user (gold).
• Inventory: Holds the resources the player has gathered.

The game can have 2 feedback loops: positive & negative: 

• Converter: exchange one resource into another. Gold for swords.
• Drain: removing resources from the economy

Lastly, a trader can act like other players, buying&selling resources at will.