Critfall

Tabletop-style d20 combat for Minecraft / fully data-driven.

Critfall turns Minecraft's damage into dice resolution. Every damaging action rolls
d20 + modifiers against the target's Armor Class. A miss deals nothing; a hit rolls damage
dice like 2d6+3 instead of a fixed number. Nat 20 crit, Nat 1 Fumble.

Core features

• Attack rolls vs Armor Class for melee, projectiles, and spells, all server-side.
• Damage dice with a full expression parser (NdM+K, keep-highest/lowest, advantage/disadvantage).
• Configurable criticals (max dice / double dice / double total) and a weighted, composable fumble
    system (durability loss, hit-nearest-ally, self-damage, drop weapon, stumble, status effects,
    knockback).
• Saving throws for AoE-style spell damage.
• Graceful fallbacks: unknown mobs derive AC from armor attributes and unknown weapons derive
    dice from attack damage, so it works in any pack with zero configuration.

Made for pack developers

• critfall generate — write a complete, editable datapack of derived profiles for every mob and
    weapon in your pack, then tune the numbers.
• critfall report — export a CSV/JSON coverage sheet (profiled vs fallback + effective values).
• Dry-run mode — see the rolls while vanilla damage still applies, to calibrate without breaking
    your pack.
• critfall inspect and critfall check — see which profile won and why.
• Every mechanic is an individual toggle; turning one off restores vanilla behavior for just that
    mechanic. Three ready-made presets: Tempered, Classic, Lite.
• Tag-driven matching with priority resolution and namespace wildcards.

For mod developers

A stable public API (studio.modroll.critfall.api) plus optional KubeJS bindings: roll dice, drive
attacks with full context, query effective profiles, fire outcome tables, and suppress the automatic
pipeline per-entity, with loader-agnostic pre/post-roll, crit, and fumble events.

Loaders

NeoForge and Fabric, Minecraft 1.21.1, with parity verified by a shared in-game test suite on both.

Compatibility

Critfall intercepts the damage event, so it sits downstream of most combat mods and composes with
them. Spell mods that tag their damage types are handled generically. Iron's Spells 'n Spellbooks and Ars Nouveau are researched and ship with targeting and tuning guidance in the docs, use that as
a tested starting point to verify in your pack, not a promise of perfect integration. That work is still in progress. Mods that bypass the damage event (direct health setting / custom pipelines) are
not intercepted.

MIT licensed. Docs, an example datapack, and JSON schemas are in the repository.