The "Target 20" core mechanic provides an elegant way to resolve actions in classic D&D without the need for table lookups, complicated math, or recording of any new statistics. The basic system is this:

Some additional information can be found on the one-sheet linked to the left. (For example, D&D monster to-hit rolls are effectively: d20+HD+AC ≥ 20.) You can also see spreadsheet analyses of the probabilities in question below.

• Attack Roll Analysis
• Saving Throw Analysis
• Thief Skill Analysis