One of the key components of fun gameplay is its unpredictability — i.e. that the ultimate outcome of a game is not known until it is played. There are four generic ways to implement unpredictability in game designnote : hidden informationnote , skill/performance-based challengesnote , opponent uncertaintynote , and randomizers — rules and mechanics that utilize some sort of a Random Number Generator (like dice or cards) to inject randomness directly into gameplay loops. Gameplay randomization comes in several distinct patterns (adapted from The Forge's fortune mechanics classification), depending on when exactly the randomness affects or informs the player's decisions:
- "Fortune at the Beginning": Generate randomness, invoke mechanic, adjudicate outcome. In this variation, randomness enters play before the player decides on their move in the current gameplay loop, which is then resolved deterministically. Great examples of this in board games are Settlers of Catan and Monopoly, where each player must roll dice at the start of their turn, before reacting and adapting to their new resources and/or position. Settlers also contains a second type of such input randomness, in its randomly determined initial board state.
- "Fortune in the Middlenote ": Invoke mechanic, generate randomness, mitigate randomness, adjudicate outcome. This variation, popular in fiction-first indie RPGs, adds an additional player decision into the loop, where they can no longer abort an action once the dice are rolled, but may spend a limited resource to offset particularly unlucky rolls before the results are finalized. This effectively allows players to steer the narrative in their preferred direction while leaving its ultimate outcome uncertain.
- "Fortune at the End" (FatE): Invoke mechanic, mitigate, then generate randomness, adjudicate outcome. This is, perhaps, the most popular way to use randomizers: you decide on your action, tally up your bonuses, roll the dice and hope for the best, because the results are now completely up to the Random Number God.
As Keith Burgun points out, however, these are not necessarily distinct categories but rather a continuum between input and output randomness, determined by the position of the randomizer relative to the player decision in a game loop. It is also true that for faster-paced gameplay, the distinction becomes very blurry, as the output randomness of one action immediately becomes the input randomness of the next.
- A.I. Roulette: When computer-controlled characters pick their behaviors at random, rather than reacting to the environment.
- Betting Mini Game: A minigame based entirely around randomness.
- Critical Failure: When you always have a small chance of randomly whiffing an attack or some other action — often dramatically so.
- Critical Hit: Although some games allow for automatic crits under certain conditions, most of the time, they happen randomly when using the attack mechanics.
- The Gambler: A character class based around randomness (more so than other classes, anyway).
- Loot Boxes: Game rewards that are completely random and unrelated to anything you actually do in the game.
- Luck-Based Mission: Typically not a single mechanic per se, but an entire level where your success or failure effectively depend on some combination of randomizer-based mechanics.
- Luck Manipulation Mechanic: A mechanic that is usually invoked after the randomness occurs, in order to mitigate it.
- Luck Stat: A character attribute that affects probabilities in the game.
- Random Drop: When what you get from a slain enemy is randomized.
- Random Effect Spell: A special ability whose effect is determined at random after it is invoked.
- Random Encounters: Usually violent interactions that occur in random places and/or at random times.
- Random Event: A narrative event pulled from a range of options to occur at a random point in the game.
- Randomized Damage Attack: When it's not enough to just hit an enemy — the damage your attack does is also randomized.
- Randomly Generated Levels: A randomness generator is used for Procedural Generation of entire game levels — note, however, that general PG does not have to be randomizer-based.
- Randomly Generated Loot: Ditto, but for Random Drops — not only are they dropped at random, their stats and special properties are randomized, as well.
- Randomly Generated Quests: Ditto, but for side quests, regarding their requirements and rewards.
- Video Game Randomizer: A mode (usually but not always a Game Mod) which randomizes major objectives in a game.