2d20 System

The 2d20 system was developed as a cinematic tabletop roleplaying game rule set by the publisher Modiphius for games based on intellectual properties like the Dune RPG, the Fallout RPG, and the Star Trek RPG. They also use it for a few of their original games, like Achtung! Cthulhu and Dreams and Machines. As you might guess, the core mechanic in the 2d20 system has players roll two twenty-sided dice. You compare these rolls to a target number, counting rolls that come up that number or lower as a success. Lower rolls are generally better in 2d20 systems! Your target number depends on the specific game, but is often based on your character's attributes, which will be higher if your character is more skilled, making it more likely to score a success. You might also have a more specific skill as a supplementary target number, and rolling under that might count as two successes! After the roll, you count your total successes and compare it to a difficulty set by the game master, usually 1 or 2, but this can go even higher for more difficult and dangerous tasks. If you have successes equal to the difficulty, you succeed! If you have fewer than you need, you fall short in some way. If you have more successes than you needed, they get converted into a currency, which differs depending on the game. In most games, you can spend this currency to activate special abilities, push your luck by rolling extra dice, and take extra actions. This currency is often called "momentum" or something similar, representing how characters can press their success! The GM also has a currency, which accumulates when players push their luck, often called "doom" or "threat," which they can spend to complicate the players' lives, introduce new problems, and generally make their lives interesting.