# skill-system

> Implements skill mechanics, balancing, and player ability handling for L2J Interlude.
Use when: creating new skills, modifying skill effects, implementing balance changes, debugging skill execution, or adding skill handlers

- Author: valeriybaranyshyn-pixel
- Repository: valeriybaranyshyn-pixel/Tales-of-Aden
- Version: 20260202145225
- Stars: 0
- Forks: 0
- Last Updated: 2026-02-06
- Source: https://github.com/valeriybaranyshyn-pixel/Tales-of-Aden
- Web: https://mule.run/skillshub/@@valeriybaranyshyn-pixel/Tales-of-Aden~skill-system:20260202145225

---

---
name: skill-system
description: |
  Implements skill mechanics, balancing, and player ability handling for L2J Interlude.
  Use when: creating new skills, modifying skill effects, implementing balance changes, debugging skill execution, or adding skill handlers
allowed-tools: Read, Edit, Write, Glob, Grep, Bash
---

# Skill System

The L2J skill system uses a layered architecture: XML definitions → SkillTable registry → ISkillHandler execution → Effect application. Skills are parsed at startup, cached in memory with a composite key (`skillId * 256 + level`), and executed through type-based handler dispatch.

## Quick Start

### Define a Physical Damage Skill (XML)

```xml
<!-- Files/game/data/xml/skills/0000-0099.xml -->
<skill id="3" levels="9" name="Power Strike">
    <table name="#power"> 25 27 30 39 42 46 60 65 70 </table>
    <table name="#mpConsume"> 10 10 11 13 13 14 17 18 19 </table>
    <set name="skillType" val="PDAM"/>
    <set name="operateType" val="OP_ACTIVE"/>
    <set name="target" val="TARGET_ONE"/>
    <set name="power" val="#power"/>
    <set name="mpConsume" val="#mpConsume"/>
    <set name="reuseDelay" val="13000"/>
    <set name="castRange" val="40"/>
</skill>
```

### Create a Skill Handler

```java
// Files/java/net/sf/l2j/gameserver/handler/skillhandlers/MyHandler.java
public class MyHandler implements ISkillHandler {
    private static final L2SkillType[] SKILL_IDS = { L2SkillType.MY_TYPE };
    
    @Override
    public void useSkill(Creature activeChar, L2Skill skill, L2Object[] targets) {
        if (activeChar.isAlikeDead()) return;
        
        for (L2Object obj : targets) {
            if (!(obj instanceof Creature)) continue;
            Creature target = (Creature) obj;
            
            int damage = (int) Formulas.calcPhysDam(activeChar, target, skill, shld, crit, ss);
            target.reduceCurrentHp(damage, activeChar, skill);
        }
    }
    
    @Override
    public L2SkillType[] getSkillIds() { return SKILL_IDS; }
}
```

### Balance a Skill (No Code Changes)

```xml
<!-- Files/game/data/balance/skills/skill_balance.xml -->
<skill id="3" name="Power Strike">
    <balance powerMul="1.25" reuseMul="0.80"/>
</skill>
```

## Key Concepts

| Concept | Location | Purpose |
|---------|----------|---------|
| L2SkillType | `templates/skills/L2SkillType.java` | Enum mapping skill types to handlers |
| SkillTable | `datatables/SkillTable.java` | Singleton registry, loads XML at startup |
| ISkillHandler | `handler/ISkillHandler.java` | Strategy interface for skill execution |
| EffectTemplate | `skills/effects/EffectTemplate.java` | Reflection-based effect factory |
| Formulas | `skills/Formulas.java` | Damage, hit chance, critical calculations |
| SkillBalanceHolder | `balance/skills/SkillBalanceHolder.java` | Runtime balance modifiers |

## Common Patterns

### Add Buff Effect with Stat Modifier

```xml
<skill id="4" levels="2" name="Dash">
    <set name="skillType" val="BUFF"/>
    <set name="target" val="TARGET_SELF"/>
    <for>
        <effect name="Buff" time="15" stackType="speed_up_special" stackOrder="1">
            <add order="0x40" stat="runSpd" val="40"/>
        </effect>
    </for>
</skill>
```

### Apply Balance Multiplier in Handler

```java
// In skill execution code
double damage = baseDamage;
double powerMul = SkillBalanceHolder.getStat(skill.getId(), "powerMul", 1.0);
damage *= powerMul;
```

## See Also

- [patterns](references/patterns.md) - Handler patterns, effect creation, conditions
- [workflows](references/workflows.md) - Adding skills, balancing, debugging

## Related Skills

- **java** skill for Java coding conventions and singleton patterns
- **xml-data** skill for XML parsing and data file structure
- **ai-system** skill for how NPCs/summons cast skills via AI intentions
- **pvp-events** skill for event-specific skill restrictions
- **database-schema** skill for skill-related database tables