Random Number Generator

About

Dice are an integral part of tabletop role-playing games (TTRPGs), serving as the primary mechanism for introducing randomness, excitement, and unpredictability into a game's narrative. They determine the outcomes of player actions, from skill checks and combat to random events and magical effects. While a set of polyhedral dice may be a common sight, the way different game systems utilize these dice varies dramatically. Understanding the core dice mechanics of a game can help players and game masters appreciate the unique feel and strategic depth of each system.

Flat Roll-Over: Aiming for a High Score

One of the most common and straightforward dice mechanics is the Flat Roll-Over system, often found in popular fantasy TTRPGs. In this system, the goal is to roll a single die and have the final result be equal to or higher than a specific target number.

Players typically roll a die, such as a 20-sided die (d20), and add a modifier based on their character's skills or stats. The Game Master sets a difficulty number, which the player's total must meet or exceed to succeed. The probability in a Flat Roll-Over system is easy to calculate, making it simple for players to gauge their chances of success before a roll. For instance, a character with a +3 modifier needing to hit a target number of 15 knows they must roll a 12 or higher on the d20 for the action to succeed.

Flat Roll-Under: The Opposite Approach

The Flat Roll-Under system is the inverse of its roll-over counterpart. Here, the objective is to roll a single die under a target value, which is usually determined by a character's skill rating or attribute score.

For example, in a percentile-based system like Call of Cthulhu, a player with a 33% skill rating must roll a 33 or lower on a d100 to succeed. The Game Master can modify the difficulty by adding or subtracting from the target number, making a task harder or easier. This mechanic can heighten psychological tension by making the failure or success of a critical action feel more personal to the player.

Dice Pool Mechanics: Rolling for Success

Unlike systems that rely on a single die, a dice pool mechanic requires players to roll multiple dice at once to resolve an action. This approach allows for more nuanced outcomes and adds another layer of complexity to the gameplay. There are two primary types of dice pool systems:

Summing Dice Pool: In this system, a player rolls a number of dice and adds up their total value. The sum is then compared to a target number to determine success or failure. The total outcome of multiple dice tends to form a bell-curve probability distribution, where middle-range numbers are more likely than extreme high or low numbers. This adds a level of unpredictability and makes the impact of character bonuses more dramatic.

Counting Dice Pool: In this system, a player rolls a pool of dice and counts how many individual dice meet a certain criterion, such as rolling a 6 or higher. The number of successful dice is then compared to a required number of successes to determine the outcome. This mechanic is often considered easier for players to manage on the fly than summing dice pools. Popular games like World of Darkness use this counting method.

Other Noteworthy Dice Systems

Some games use hybrid or specialized mechanics that combine elements of the systems above. For instance, the "One of Dice Pool" system involves rolling multiple dice but only taking one of the results. An example is the advantage and disadvantage mechanic, where a player rolls two d20s and takes the highest result for an advantage or the lowest for a disadvantage. This increases the odds of success or failure without changing the target number.

Ultimately, the choice of a dice mechanic is a fundamental design decision that shapes the entire TTRPG experience. Whether a game focuses on the high-stakes roll of a single die or the statistical spread of a large dice pool, the result is an unpredictable, engaging journey for players and game masters alike.