In an economic system, players can generate, consume/destroy, or trade resources in a zero-sum fashion (what a player consumes is what another can not consume). Supply and demand curves:
- supply = f(price) is monotonic (increasing): if I sell for $5, then I also can sell for $10
- demand = f(price) is decreasing: if I accept to buy for $10, I also accept to buy for $5
Market price = where the 2 curves intersect. Prices fluctuate as players need or produce items. Prices fluctuate more if there are fewer players. Demand curves affect each other:
- substitutes: SP potion (+ casting Heal spell) is a substitute for HP potion. Increasing supply of X means decreasing demand of Y.
- item sets/collectibles: when together, sword X + shield Y give +10atk bonus. Increasing supply of X means increasing demand of Y.
The price per unit can increase or decrease depending on how many of that unit the player already has. If more units of the same kind brings increasing bonuses, then marginal cost decreases. If each unit costs more and more, the game is more stable and homogeneous.
Demand increases with scarcity. Example in FPS: ammo can be limited (player don't shot all the time, therefore it'd make sense if they died in one shot) or infinite (trigger happy, players should only loose a bit of life when they're hurt). In RTS, limited number of mines to get gold from means shorter games, whereas more and bigger mines means longer games (and more military encounters).
Closed-system = game systems that are self-contained, nothing outside of them can influence what's inside. Somehow, gold farmers open the closed economies of MMOGs, making them harder to design and control. The game should not allow players who have more RL money to have more power, it should just allow more options/variety. Experts using cheap/default CCG decks should beat novices using expensive/rare decks. Yet RL money could be used to speed up progression/avoid grinding.
Inflation happens in MMOs because the game is positive sum (money comes from quests and monsters). New players will never catch up unless negative-sum (sinks) or zero-sum elements are included. Negative-sum/Sinks can be: NPC, repair and death penalties, luxury items, or even tax richest players and give that money to poor players (Robin Hood transforming positive-sum into zero-sum). Zero-sum can be: player-bound/non-tradable items, quests can be repeated but reward only once. Nothing tradable also is a solution.
By giving players resources they do not need, they'll have an incentive to trade. Trading mechanics usually serve as a negative-feedback loop, especially within a closed economy. Players are generally more willing to offer favorable trades to those who are behind, while they expect to get a better deal from someone who is ahead (or else they won’t trade at all).
- future agreements: I give X now for Y now and Z later. Players could renege, making them more suspicious when trading with delays.
- scope: powerful resources (eg victory points in Catan) should not be tradable. Tradable resources become more fluid.
- time and phases: players can trade all the time, and trades could take effect at once. Or trading could be limited to certain phases (every 5 turns, or before player starts his building phase) and/or this phase could be timed (eg 5-min timer to bargain).
- evenness: gifts (0 for n) vs even trades (1 for 1) vs uneven trades (1 for n)
- quantification: trading can happen only once per turn/per hour, or as much as player wants. Number of exchanged objects may be bounded as well.
- tax: if trading coalitions are too powerful, put a tax as a cost to trade
- forced: I look at the cards in your hand and pick the best, and give you in exchange my worse card.
Auctions = players' willingness to pay for a resource. Auctions work best when the actual cost is variable, different between players, and situational. Each time players decide how much the resource is worth to them, they are making an «interesting choice».
- Many types of auctions (increasing, blind, decreasing, ...),
- with different kinds of rewards (winner gets the entire lot, or first pick in the draft, and/or looser gets bonus or penalty),
- different payers (top bidder, top 2 bidders, top and bottom bidders, all players, ...),
- different recipients (bank = deflation, shared fund, or to other players),
- different events when no one bids (resource given to a random player, or more resources are added to the current resource and the auction restart, or resource is just discarded)
|Turtling||Everybody shelters and nobody actually plays because attacking seems more costly and inefficient than defending and waiting for opportunities.||Give incentives to attack (when players wins, she gets more resources next turn), or force players to attack (player has to draw and play one card each turn, and 90% of cards are attack cards).|
|Kill the leader and sandbagging||Hidden scores make it impossible to know who is the leader, or make it obvious that eliminating the leader is not the best chance to win, or make the game non-PVP, or make players not able to team-up against another/give advantage when a player defends against many|
|Kingmaking||Make players believe they can always win, or make it impossible to know which action will make a king, or make it impossible to choose who to make king, or simply do not allow last players to help leaders|
|Elimination||Player is killed at the beginning of the game and has to wait for the game to end||Players can only eliminate others if they are strong enough to eliminate all others, or the goal can be to collect points (instead of killing others), or when one player dies, the game stops immediately or within a certain time, and winner is current leader, or make the killed player take control of NPC, or make it interesting to look at other players playing (cf Mafia or Werewolf), or let killed players have goals as well (Cosmic Encounter or BSG)|
Final note: balance is not always a must-have. Some games are ostensibly unfair but fun nevertheless. In single-player games, progression matters more than fairness. The unfairness of some one-against-many multiplayer games sometimes makes them fun.