Target 20 System

Abstract

Target 20 is a simplification framework for classic D&D play that replaces table lookups and descending-target arithmetic with one constant rule: roll a d20, add level and relevant modifiers, and succeed on 20 or more. It preserves core assumptions of OD&D/B/X style play while reducing cognitive load at the table.

Core Rule

d20 + level (or HD) + modifiers >= 20 succeeds.

The target number never changes. Difficulty is expressed through modifiers (such as armor class in descending AC systems), not through shifting DCs.

Attack Resolution

Fighters and monsters add full level/HD.
Clerics and thieves are typically treated as two-thirds level.
Magic-users are typically treated as half level.
Descending AC is added directly to the roll, so better armor contributes less to attacker totals.

This keeps monster attacks table-free as well, because HD already exists on stat blocks.

Saving Throws

Saving throws are resolved with the same Target 20 core:

d20 + character level + save-type modifier >= 20

Example save-type modifiers in the source are ordered from weaker to stronger categories (+0 to +4), enabling one formula instead of class-level save matrices.

Some classless B/X variants prefer Nd6 roll-under saves instead of Target 20. This section documents the source's system for reference only.

Thief Skills

Thief skills can be collapsed into the same structure:

d20 + thief level + ability modifier >= 20

This avoids maintaining percentile skill tables while preserving level scaling.

Accuracy Claims

The source argues Target 20 tracks closely with original matrix outcomes, often within one or two pips. At first level, attack outcomes are noted as effectively identical to OD&D tables, with divergence increasing gradually at higher levels.

Design Implications

Unified procedure: One resolution style across combat, saves, and skills.
Lower lookup overhead: Less matrix checking during play.
Table compatibility: Works with existing descending AC and HD statlines.
Tradeoff: Exact legacy probabilities are approximated rather than reproduced verbatim.