What is game balance:
- for single player games, it is difficulty, pacing, character progression
- for multiplayer, advantage at the beginning of the game, strategies (any strategy could be viable OR some are more viable than others (could be overpowered)) or game objects
How to balance a game:
- intuition (from experience, not teachable),
- playtesting (statistical analysis, rely on player skill: novices could never find a needed good strategy),
- math (numbers are everywhere in games)
Playtest is really needed for interconnected systems, because modifications can have rippled effects.
Player skill can make a difference in exploiting an imbalance.
Some game vocabulary
- deterministic. Deterministic + perfect information = solvable.
- solvable: has a single, knowable “best” action to take at any given point in play, and the player can know this action (it is undesired in games if it's trivial); including humans in the loop (like in Poker) fixes the problem of solvability
- intransitive (eg in rock paper scissors, paper > rock and rock > scissors, but paper is not > scissors)
- symmetric (means balance at the beginning, but not between game objects or strategies)
- metagame: can be balanced as well, and definitely affects the game balance: drafting and rarity for trading card games, analyzing opponents' strategies to win the next Poker game, capping the salary of sport players so that most clubs can afford recruiting them
When trying to fix an unbalance, ask where it really comes from
If you do not know how much an advantage a beginning side is in a RTS like Warcraft3, you can let the playtesters bid in auctions for their beginning side. Knowing how much they give makes you know how much is necessary to balance the beginning state.
Allowing players to cooperate to kill the strongest player can balance a diplomacy game, but also sometimes only make it last longer and be more annoying (players do not want to appear too strong)