IDK: I Don't Know - The Role-Playing Game was developed to be a simple system suited to single-night play, though it could be used in a more-traditional campaign setting. The rules allow an adventure that can be designed and run with little preparation.
Players allocate 400 percentage points among twelve skills (Combat, Remain Calm, Persuasion, Notice, React Fast, Skulk, Transport, Cogitate, Education, Endure Suffering, Athletics, and Enigma). Specialties may be selected, and they have an impact on skills. Players may not allocate more than 65% into any one skill and should take less than 25% in any skill only with caution. Skill checks are made by rolling percentile dice and rolling under the character's score in the appropriate skill.