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Introduction

Welcome to Mod-Engine - a powerful TypeScript library for building type-safe attribute and modifier systems with deterministic evaluation.

What is Mod-Engine?​

Mod-Engine provides a complete framework for creating complex item modification systems commonly found in RPGs, simulations, and other applications requiring dynamic attribute calculations. It offers:

  • 🎯 Type Safety - Full TypeScript support with intelligent autocompletion
  • ⚡ Performance - Optimized evaluation engine with minimal overhead
  • 🔧 Flexibility - Support for complex conditions, priorities, and stacking rules
  • 📊 Deterministic - Consistent, reproducible results every time
  • 🛠️ Developer Friendly - Intuitive API with comprehensive error handling

Key Features​

Type-Safe Configuration​

Define your metrics, operations, and attributes with full TypeScript support:

const config = defineConfig({
  metrics: ["Health", "Damage", "Defense"] as const,
  operations: ["sum", "multiply", "subtract"] as const,
  attributes: [
    {
      key: "Rarity",
      kind: "enum",
      values: ["Common", "Rare", "Epic", "Legendary"] as const,
    },
  ] as const,
});

Flexible Modifier System​

Create modifiers with conditional logic and priority ordering:

const sword = engine
  .builder("Legendary Sword")
  .set("Rarity", "Legendary")
  .increase("Damage")
  .by(100)
  .when({ op: "eq", attr: "Rarity", value: "Legendary" })
  .multiply("Damage")
  .by(1.5)
  .build();

Deterministic Evaluation​

Get consistent results with complete audit trails:

const result = engine.evaluate(sword);
console.log(result.metrics); // { Health: 0, Damage: 150, Defense: 0 }
console.log(result.trace); // Complete evaluation history

Use Cases​

Mod-Engine is perfect for:

  • RPG Systems - Character stats, equipment bonuses, spell effects
  • Game Development - Item modifications, buff/debuff systems
  • Simulation - Dynamic property calculations with complex rules
  • Configuration Systems - Type-safe rule engines with validation

Getting Started​

Ready to dive in? Check out our Installation Guide and Quick Start to begin building with Mod-Engine.

For a complete working example, try our Next.js Interactive Demo.