Editing GURPS (section)

===Success rolls===
''GURPS'' uses six-sided [[dice]] for all game mechanics using [[dice notation|standard dice notation]]. An [[Median|"average roll"]] of three six sided dice generates a total of 10.5; this makes an "average" skill check (a skill of 10, based on an unmodified attribute) equally likely to succeed or fail.

Making statistic and skill checks in ''GURPS'' is the reverse of the mechanics of most other RPGs, where the higher the total of the die roll, the better. ''GURPS'' players hope to roll as low as possible under the tested statistic's rating or skill's level. If the roll is less than or equal to that number, the check succeeds. There is no "target number" or "difficulty rating" set by the Game Master, as would be the case in many other RPG systems. Instead the GM will apply various modifiers to add or subtract to the skill level. In this way, positive modifiers increase the chance for success by adding to the stat or skill level the player must roll under while negative modifiers deduct from it, making things more difficult.

For example: a player makes a pick pocketing test for her character. The character has a Pickpocket skill with a level of 11. Under normal circumstances - i.e., under an ''average stressful situation'', according to the manual - the player must roll an 11 or less for the character to succeed. If the player rolls above 11, then the character has failed the attempt at pick pocketing.

There are some exceptions for very high or low rolls, deemed [[Critical hit|criticals]]. No matter the level of the skill, a die roll of 18 is always a ''critical failure'', and a roll of 3 or 4 is always a critical success (a roll of 17 is a critical failure as well, unless the character relevant skill level is 16 or more). The Game Master may decide in such cases that, in first case (a roll of 18, or 10+ over the modified skill level), the character has failed miserably and caused something disastrous to happen or, in the other case, that he or she succeeds incredibly well and gains some benefit as a result.