All game systems consist of elements in a constant flow of Resources.
Resources can be anything from money and property in Monopoly, ammo and HP in an FPS, or XP and equipment in an RPG.
Resources, together with the entities or actions that cause them to be produced, consumed and exchanged, make up the games' internal economy.
Any Resource flow can be represented in a Machinations diagram.
Entities are represented by Nodes and the way in which Resources are produced, consumed and exchanged is determined by Connections.