Technical Architecture & Mixins Breakdown

Component	Specification
Architectural Law	1 File, 1 Function Law (Single-purpose classes)
Mixin Framework	SpongePowered Mixin for Fabric Loom 1.15.5
Java Platform	Java 25
Thread Safety	Non-blocking main thread execution

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📂 ASCII Package Architecture

net.vanillaoutsider.naturalreproduction
│
├── NaturalReproductionFabric.java       # Mod initialize entrypoint & GameRules registration
├── ModVersionGuard.java                 # Zero-dependency startup class guard (Knot ClassLoader)
│
├── client/
│   ├── ModMenuIntegration.java          # ModMenu API entrypoint
│   └── YaclScreenHelper.java            # YACL v3 config screen builder
│
├── command/
│   └── NaturalReproductionCommand.java  # Brigadier command suite (/naturalreproduction)
│
├── mixin/
│   ├── AnimalBreedingMixin.java         # Autonomous love mode tick injection & genetics inheritance
│   └── AnimalDropScaleMixin.java        # Scale-proportional item drop yield injection
│
└── util/
    ├── AnimalBiomeHelper.java           # Native climate biomes & skin variant triggers
    ├── AnimalCrampedSpaceHelper.java    # Dual structural confinement & density crowding penalty
    ├── AnimalDropHelper.java            # Scale-based item drop yield multiplier logic
    ├── AnimalHabitatHelper.java         # 27 species environmental habitat block scanning
    ├── BreedingLogEntry.java            # Event tracking data structure
    └── BreedingTrackerLogger.java       # In-memory breeding event logger

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⚙️ Java Mixins Target Breakdown

Mixin Class	Target Minecraft Class	Target Method / Injection Point	Description
AnimalBreedingMixin	net.minecraft.world.entity.animal.Animal	@Inject into customServerAiStep (HEAD) & spawnChildFromBreeding (TAIL)	Evaluates autonomous Love Mode conditions (health, partner proximity, overcrowding density cap, habitat blocks, species toggles) and handles baby scale inheritance/cramped stunting.
AnimalDropScaleMixin	net.minecraft.world.entity.Entity	@Inject into spawnAtLocation (HEAD)	Intercepts entity item drop spawning and delegates to AnimalDropHelper.applyScaleDropMultiplier when SCALE_DROPS GameRule is enabled.

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🛠️ Helper Utilities Architecture

1. AnimalHabitatHelper.java

• Scans a 5x3x5 cuboid (offset(-2, -1, -2) to offset(2, 1, 2)) around the entity for required environmental habitat blocks across all 27 animal species.
• Evaluates isSpeciesReproductionAllowed(level, self) against the natural_reproduction_species GameRules.

2. AnimalCrampedSpaceHelper.java

• Dual Confinement Check:
  • isConfinedArea(level, pos): Detects horizontal 1x1 / 2x2 pit holes, fences, walls, and solid block enclosures (3+ blocked sides).
  • isOvercrowded = isConfinedPen || extraLocalCount >= 3: Applies crowding penalty both in tight structural pens AND in large open pastures (e.g. 100x100) when animals are crammed together.
• Smooth Continuous Penalty Formula: $$\text{penaltyMultiplier} = \max(0.95 - (\text{extraLocalCount} \times 0.05), 0.40)$$

For API integration, see API & Addon Integration.