[Engine] Dice Mechanics

[Steven]

Dice Mechanics
Overview
This RPG uses percentile dice (a pair of d10s or a single 100-sided die) for most skill-based and combat activities, supplemented with miscellaneous dice for things like damage rolls. Your GM may choose to use the Quick-n-Dirty die-rolling system (which uses a 20-sided die instead of percentile dice) as explained in the GM’s Guide. If you possess enough manual dexterity to roll a pair of dice, either method should be simple enough for even the greenest pen-and-paper player. If you have difficulty with the dice, you can ask your GM to roll for you. He/she probably won’t cheat.

Details
Most activities are handled using a percentile-based system of 0-100%. This percentage is used as a 'Chance to Fail'. Beat it and you succeed. Rolls are typically made with a d20, the result of which is multiplied times 5 to produce a number ranging from 5 to 100. An activity with a difficulty of 100% is effectively impossible without some intervening factor, such as a power that lowers the difficulty by 5%.

Typically, during activities requiring the use of a particular skill, the difficulty class of the activity is only used if it is higher than the player's chance to fail at the appropriate skill. The two numbers are NOT combined unless the difficulty class is specifically an Additive difficulty (meaning that the activity is specifically difficult to people trained in a particular skill).


Gameplay Examples
Example (Normal): a player is attempting to disarm a bomb. The bomb's difficulty rating is at 50%. The player's Disable Device skill is at 70%, however, meaning they already have a greater change of failing due to their own lack of skill. The player rolls a 15 on a d20: 75%. They have beaten both their own failure chance and the bomb's difficulty rating.

Example (Additive): a player is attempting to ride a horse. The horse has an Additive difficulty rating of 25%, because the animal in question has a particular knack for throwing experienced riders off. The player's failure chance for Transportation is at 50%. The player rolls a 12 on a d20, giving them a 60, but since the total difficulty is 75%, the attempt fails.