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+# Biome Classification
+
+> Complete specification for the BiomeClassifier: tile state to biome_id mapping for all 25+ biomes, including aquatic sub-classification and subterranean detection.
+
+---
+
+## Biome Inventory (26 biomes)
+
+### Aquatic (8 biomes)
+
+| # | Biome | Quality Range | Substrate | Temperature | Moisture | Key Discriminator |
+|---|-------|-------------|-----------|-------------|----------|-------------------|
+| 1 | `deep_ocean` | Q1-Q4 | deep_water | any | n/a | depth_from_coast > 3 |
+| 2 | `shallow_ocean` | Q1-Q5 | shallow_water | any | n/a | depth_from_coast <= 3, not tropical |
+| 3 | `coral_reef` | Q1-Q5 | shallow_water | >0.55 | n/a | tropical shallow, depth_from_coast <= 2 |
+| 4 | `estuary` | Q1-Q4 | shallow_water | any | high | river mouth: adjacent to river AND ocean |
+| 5 | `lake` | Q1-Q4 | lake_bed | any | n/a | water body size >= 2 |
+| 6 | `pond` | Q1-Q2 | lake_bed | any | n/a | water body size == 1 |
+| 7 | `river` | Q1-Q3 | linear water | any | n/a | linear water body type |
+| 8 | `mangrove` | Q1-Q4 | wetland + coastal | >0.55 | high | tropical + coastal + wetland substrate |
+
+### Tropical (4 biomes, temp > 0.55)
+
+| # | Biome | Quality Range | Substrate | Temperature | Moisture | Key Discriminator |
+|---|-------|-------------|-----------|-------------|----------|-------------------|
+| 9 | `tropical_rainforest` | Q1-Q5 | lowland/midland | >0.65 | >0.7 | hot + very wet + canopy > 0.6 |
+| 10 | `tropical_dry_forest` | Q1-Q4 | lowland/midland | >0.55 | 0.4-0.7 | tropical + moderate moisture |
+| 11 | `savanna` | Q1-Q3 | lowland/midland | >0.55 | 0.15-0.4 | tropical + low-moderate moisture |
+| 12 | `desert` | Q1-Q3 | lowland/midland/arid | >0.55 | <0.15 | hot + very dry |
+
+### Temperate (5 biomes, temp 0.25-0.55)
+
+| # | Biome | Quality Range | Substrate | Temperature | Moisture | Key Discriminator |
+|---|-------|-------------|-----------|-------------|----------|-------------------|
+| 13 | `temperate_forest` | Q1-Q5 | lowland/midland | 0.25-0.55 | >0.5 | canopy > 0.5 |
+| 14 | `temperate_grassland` | Q1-Q4 | lowland/midland | 0.25-0.55 | 0.3-0.5 | moderate moisture, low canopy |
+| 15 | `chaparral` | Q1-Q3 | midland | 0.25-0.55 | 0.15-0.35 | dry-moderate, scrubland |
+| 16 | `swamp` | Q1-Q4 | wetland | >0.4 | >0.8 | saturated + warm |
+| 17 | `bog` | Q1-Q3 | wetland | <0.4 | >0.7 | saturated + cool |
+
+### Cold (3 biomes, temp < 0.25)
+
+| # | Biome | Quality Range | Substrate | Temperature | Moisture | Key Discriminator |
+|---|-------|-------------|-----------|-------------|----------|-------------------|
+| 18 | `boreal_forest` | Q1-Q4 | lowland/midland | 0.1-0.25 | >0.35 | cool + moderate moisture + canopy > 0.3 |
+| 19 | `tundra` | Q1-Q3 | lowland/midland | 0.05-0.15 | any | cold, minimal flora |
+| 20 | `polar_desert` | Q1-Q2 | any | <0.05 | any | extreme cold |
+
+### Elevation (5 biomes)
+
+| # | Biome | Quality Range | Substrate | Temperature | Moisture | Key Discriminator |
+|---|-------|-------------|-----------|-------------|----------|-------------------|
+| 21 | `montane_forest` | Q1-Q4 | highland | 0.2-0.45 | >0.4 | highland + canopy > 0.4 |
+| 22 | `cloud_forest` | Q1-Q5 | highland | 0.25-0.45 | >0.7 | highland + very wet |
+| 23 | `alpine_meadow` | Q1-Q3 | mountain | any | >0.3 | above treeline + moderate moisture |
+| 24 | `alpine_tundra` | Q1-Q2 | mountain/peak | any | <0.3 | above treeline + dry |
+| 25 | `permanent_ice` | Q1-Q1 | peak | <0.1 | any | summit + extreme cold |
+
+### Special (1 biome)
+
+| # | Biome | Quality Range | Substrate | Temperature | Moisture | Key Discriminator |
+|---|-------|-------------|-----------|-------------|----------|-------------------|
+| 26 | `subterranean` | Q1-Q4 | mountain/peak | any | any | has_cave == true (map gen marker) |
+
+---
+
+## Classification Algorithm
+
+### Top-Level Dispatch
+
+```
+BiomeClassifier.classify(tile) -> biome_id:
+  if tile.has_cave:
+    return "subterranean"
+  if tile.is_water:
+    return _classify_aquatic(tile)
+  if tile.substrate_id == "volcanic":
+    return "volcanic"  # special substrate, not a biome per se
+  return _classify_land(tile)
+```
+
+### Aquatic Sub-Classification
+
+The aquatic classifier handles 8 water biomes with priority-ordered checks. Order matters: more specific biomes (estuary, mangrove, coral_reef) must be checked before generic ones (shallow_ocean, deep_ocean).
+
+```
+_classify_aquatic(tile) -> biome_id:
+  # 1. Inland water bodies (identified at map gen)
+  if tile.water_body.type == "pond":
+    return "pond"
+  if tile.water_body.type == "river":
+    return "river"
+  if tile.water_body.type == "lake":
+    return "lake"
+
+  # 2. Estuary: river mouth detection
+  #    A tile is an estuary if it is ocean/sea water AND
+  #    at least one neighbor is a river tile or river-mouth-flagged
+  if _is_ocean(tile) and _has_adjacent_river_mouth(tile):
+    return "estuary"
+
+  # 3. Mangrove: tropical + coastal + wetland
+  #    Technically a coastal biome, classified on the water side
+  #    where shallow water meets tropical wetland
+  if tile.depth_from_coast <= 1 and tile.temperature > 0.55:
+    if _has_adjacent_wetland(tile):
+      return "mangrove"
+
+  # 4. Coral reef: tropical shallow water
+  if tile.temperature > 0.55 and tile.depth_from_coast <= 2:
+    return "coral_reef"
+
+  # 5. Depth-based ocean classification
+  if tile.depth_from_coast <= 3:
+    return "shallow_ocean"
+  return "deep_ocean"
+```
+
+**River mouth detection**: A tile has `_has_adjacent_river_mouth` if any of its hex neighbors is:
+- A river tile (water_body.type == "river"), OR
+- A land tile with `river_exit == true` (set by hydrology generation when a river flows into the ocean)
+
+**Adjacent wetland detection**: `_has_adjacent_wetland` checks if any hex neighbor is a land tile with `substrate_id == "wetland"`.
+
+### Land Classification
+
+Land classification uses a priority cascade: wetland override, then elevation, then temperature, then moisture.
+
+```
+_classify_land(tile) -> biome_id:
+  temp = tile.temperature
+  moisture = tile.moisture
+  elevation = tile.elevation
+  canopy = tile.canopy_cover
+
+  # --- Wetland override (saturated lowlands) ---
+  if tile.substrate_id == "wetland" or (moisture > 0.7 and elevation < 0.4):
+    if temp > 0.4:
+      return "swamp"
+    return "bog"
+
+  # --- Elevation-driven (highland/mountain/peak) ---
+  if elevation > 0.85:
+    if temp < 0.1:
+      return "permanent_ice"
+    return "alpine_tundra"
+
+  if elevation > 0.70:
+    if moisture > 0.3 and canopy > 0.2:
+      return "alpine_meadow"
+    return "alpine_tundra"
+
+  if elevation > 0.55:
+    if moisture > 0.7 and temp > 0.25:
+      return "cloud_forest"
+    if canopy > 0.4:
+      return "montane_forest"
+    if moisture > 0.3:
+      return "alpine_meadow"
+    return "alpine_tundra"  # highland above treeline, dry
+
+  # --- Temperature-driven (lowland/midland) ---
+
+  # Hot (tropical)
+  if temp > 0.55:
+    if moisture > 0.7 and canopy > 0.6:
+      return "tropical_rainforest"
+    if moisture > 0.4:
+      return "tropical_dry_forest"
+    if moisture > 0.15:
+      return "savanna"
+    return "desert"
+
+  # Temperate
+  if temp > 0.25:
+    if canopy > 0.5 and moisture > 0.5:
+      return "temperate_forest"
+    if moisture > 0.3:
+      return "temperate_grassland"
+    return "chaparral"
+
+  # Cool
+  if temp > 0.1:
+    if canopy > 0.3 and moisture > 0.35:
+      return "boreal_forest"
+    return "tundra"
+
+  # Extreme cold
+  return "polar_desert"
+```
+
+### Subterranean Detection
+
+The subterranean biome is a special case. Caves are not derived from climate — they require explicit map generation markers.
+
+**Detection criteria**: `tile.has_cave == true`
+
+**Map generation sets `has_cave`** on tiles meeting:
+- `elevation > 0.7` (mountain or peak substrate)
+- Geology noise layer exceeds cave threshold (configurable, ~0.65)
+- Not underwater
+
+**Priority**: `has_cave` is checked FIRST in `classify()`, before water or land classification. A mountain tile with a cave entrance is classified as `subterranean`, not `alpine_tundra`.
+
+**Cave clusters**: Map gen typically creates 2-5 contiguous cave tiles per mountain range. Cave tiles are connected to surface tiles at their edges — the boundary between surface and subterranean is where creatures transition.
+
+**Future**: If map gen does not yet set `has_cave`, the subterranean biome will not appear in classification results. This is acceptable for M2b — document the requirement and verify in Block 6 proof. If absent, the proof documents what map gen changes are needed.
+
+---
+
+## Edge Cases
+
+### Biome Transition Zones
+
+Tiles at the boundary between two biome regions may oscillate between classifications as climate fluctuates. This is intentional — biome boundaries are not hard lines in nature.
+
+**Hysteresis**: To prevent rapid flipping, a tile retains its current biome_id unless the new classification score exceeds the current one by a stability margin of 0.05 on the controlling variable (temperature or moisture). Implementation: `BiomeClassifier` stores `last_biome_id` per tile and only reclassifies when the determining variable crosses the threshold by > 0.05.
+
+### Ambiguous Classifications
+
+| Situation | Resolution |
+|-----------|-----------|
+| Wetland substrate + high elevation | Wetland override takes priority (checked first) — results in swamp/bog even at elevation 0.5. Wetland substrate overrides elevation. |
+| Highland + very wet + tropical | `cloud_forest` (elevation > 0.55, moisture > 0.7, temp > 0.25) |
+| Highland + dry + cold | `alpine_tundra` (elevation > 0.55, moisture < 0.3) |
+| Lowland + extreme cold | `polar_desert` (temp < 0.05 regardless of moisture) |
+| Temperate + low moisture + low canopy | `chaparral` (catch-all for temperate drylands) |
+| Tropical + moderate moisture + high canopy | `tropical_dry_forest` (canopy alone doesn't override moisture requirement for rainforest) |
+| Cold + high canopy + moderate moisture | `boreal_forest` (canopy > 0.3, moisture > 0.35, temp 0.1-0.25) |
+| Cold + high canopy + low moisture | `tundra` (moisture < 0.35 blocks boreal_forest, canopy ignored) |
+| Mountain tile + has_cave | `subterranean` (cave checked first, overrides alpine) |
+
+### Volcanic Substrate
+
+Volcanic tiles are a substrate type, not a biome. The classifier returns `"volcanic"` as a special case. Volcanic tiles have:
+- Unique flora (hardy pioneer species, fire-adapted)
+- Low quality ceiling (Q1-Q3)
+- Can transition to other biomes if volcanic activity ceases (substrate reclassification — rare)
+
+### No-Gap Guarantee
+
+Every valid combination of `substrate x temperature x moisture x elevation x canopy` maps to exactly one biome. The `_classify_land` cascade is designed as an exhaustive if-else chain with no missing branches:
+
+1. Wetland override catches saturated lowlands
+2. Elevation cascade catches highland/mountain/peak
+3. Temperature cascade catches tropical/temperate/cold/polar
+4. Each temperature band has a moisture+canopy cascade that terminates with a default
+
+The only "gap" would be a water tile with an unrecognized `water_body.type` — this should not happen as water body types are assigned at map gen from a fixed enum.
+
+---
+
+## Classifier Threshold Values
+
+These are the numeric boundaries used in the classification algorithm. Collected here for tuning reference.
+
+### Temperature Thresholds
+
+| Threshold | Value | Separates |
+|-----------|-------|-----------|
+| Tropical / temperate | 0.55 | tropical biomes above, temperate below |
+| Rainforest (hot) | 0.65 | tropical_rainforest requires >0.65, dry_forest needs only >0.55 |
+| Temperate / cool | 0.25 | temperate biomes above, cold below |
+| Cool / cold | 0.1 | boreal/tundra above, polar below |
+| Extreme cold | 0.05 | polar_desert below |
+| Permanent ice | 0.1 | permanent_ice at peak elevation when temp <0.1 |
+| Cloud forest min | 0.25 | cloud_forest requires temp >0.25 (not too cold) |
+| Swamp min | 0.4 | swamp requires temp >0.4 (warm enough for swamp ecology) |
+| Coral reef min | 0.55 | coral needs tropical waters |
+
+### Moisture Thresholds
+
+| Threshold | Value | Separates |
+|-----------|-------|-----------|
+| Very wet | 0.7 | tropical_rainforest, cloud_forest, bog, wetland override |
+| Wet | 0.5 | temperate_forest |
+| Moderate-wet | 0.4 | tropical_dry_forest |
+| Moderate | 0.35 | boreal_forest, temperate_grassland |
+| Moderate-dry | 0.3 | alpine_meadow, temperate_grassland |
+| Dry | 0.15 | savanna / desert boundary |
+| Saturated (wetland) | 0.8 | swamp (must exceed 0.7 for wetland override + be on wetland substrate or >0.7) |
+
+### Elevation Thresholds
+
+| Threshold | Value | Separates |
+|-----------|-------|-----------|
+| Peak | 0.85 | permanent_ice / alpine_tundra |
+| Mountain | 0.70 | alpine_meadow / alpine_tundra |
+| Highland | 0.55 | montane_forest / cloud_forest / alpine |
+| Wetland ceiling | 0.4 | wetland override only applies below 0.4 |
+| Cave eligibility | 0.7 | has_cave requires elevation > 0.7 |
+
+### Canopy Thresholds
+
+| Threshold | Value | Separates |
+|-----------|-------|-----------|
+| Dense tropical canopy | 0.6 | tropical_rainforest (with moisture >0.7) |
+| Forest canopy | 0.5 | temperate_forest |
+| Montane canopy | 0.4 | montane_forest |
+| Boreal canopy | 0.3 | boreal_forest |
+| Alpine meadow canopy | 0.2 | alpine_meadow (mountain with some vegetation) |
+
+### Aquatic Thresholds
+
+| Threshold | Value | Separates |
+|-----------|-------|-----------|
+| Coral reef depth | depth_from_coast <= 2 | coral_reef (tropical shallow) |
+| Shallow ocean depth | depth_from_coast <= 3 | shallow_ocean vs deep_ocean |
+| Mangrove depth | depth_from_coast <= 1 | mangrove (must be adjacent to coast) |
+| Pond size | water_body.size == 1 | pond vs lake |
+| Lake size | water_body.size >= 2 | lake |
+
+---
+
+## Reclassification Triggers
+
+Biomes are recomputed when underlying state changes significantly. Not every turn — only when a controlling variable crosses a threshold.
+
+### Trigger Conditions
+
+| Variable | Threshold Delta | Triggers |
+|----------|----------------|---------|
+| `temperature` | > 0.05 from last classification | Full reclassification |
+| `moisture` | > 0.05 from last classification | Full reclassification |
+| `canopy_cover` | > 0.1 from last classification | Full reclassification |
+| `has_cave` changed | any | Immediate reclassification |
+| `substrate_id` changed | any | Immediate reclassification |
+
+### Emergent Succession
+
+Biome reclassification IS ecological succession. No separate succession system needed:
+
+- Grassland with growing canopy (>0.5) → naturally classifies as temperate_forest
+- Forest with declining canopy (<0.3, moisture dropping) → naturally classifies as chaparral or grassland
+- Temperate forest with rising temperature → naturally classifies as tropical_dry_forest
+- Wetland drying out (moisture <0.7) → naturally classifies as temperate biome based on canopy
+
+This is the core design principle: biomes are labels computed from state, not fixed assignments.
+
+---
+
+## Data File Schema
+
+### biomes.json
+
+Each biome definition in `data/world/biomes/biomes.json`:
+
+```json
+{
+  "id": "temperate_forest",
+  "name": "Temperate Forest",
+  "quality_range": [1, 5],
+  "temp_range": [0.25, 0.55],
+  "moisture_range": [0.5, 1.0],
+  "substrate_types": ["lowland", "midland"],
+  "flora_climax": {
+    "canopy": 0.85,
+    "undergrowth": 0.6,
+    "fungi": 0.35
+  },
+  "fauna_capacity": 1.0,
+  "food_web_tier": "full"
+}
+```
+
+### classification.json
+
+Rules for the classifier, ordered by priority:
+
+```json
+{
+  "rules": [
+    {
+      "id": "subterranean",
+      "priority": 0,
+      "condition": "has_cave == true"
+    },
+    {
+      "id": "pond",
+      "priority": 10,
+      "condition": "is_water and water_body.type == 'pond'"
+    },
+    {
+      "id": "estuary",
+      "priority": 15,
+      "condition": "is_ocean and has_adjacent_river_mouth"
+    }
+  ]
+}
+```
+
+Rules are evaluated in priority order (lower number = higher priority). First match wins.
diff --git a/games/age-of-dwarves/docs/design/FOOD_WEB_BALANCE.md b/games/age-of-dwarves/docs/design/FOOD_WEB_BALANCE.md
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+# Food Web Balance
+
+> Tuning methodology for population stability across all 25+ biomes. Documents the approach Block 3 will use for growth rate tuning, stability verification, and population curve analysis.
+
+---
+
+## Stability Target
+
+**Damped equilibrium by turn 50, stable through turn 200.**
+
+Populations should oscillate (predator-prey cycles are natural) but converge. No mass extinction, no runaway growth.
+
+### Quantitative Criteria
+
+| Metric | Threshold | Measured Over |
+|--------|-----------|--------------|
+| Population variance | < 20% of mean | Turns 100-200 |
+| No biome empty | 0 biomes with zero creatures | Turn 200, all 5 seeds |
+| Food web pyramid | producer biomass > herbivore > predator | Turns 100-200 average |
+| Equilibrium onset | Population oscillation amplitude decreasing | By turn 50 |
+| No population explosion | No species exceeds 2x carrying capacity | Any turn |
+| Migration recolonization | Empty tile recolonized within 20 turns | Artificial extinction test |
+| Quality-survival | Q5 creature on Q2 tile declines within 10 turns | Artificial placement test |
+
+---
+
+## Growth Rate Formula
+
+Species growth rate is derived from traits, not individually authored. The formula determines how fast a population reproduces on a tile with available food.
+
+### Base Growth Rate Derivation
+
+```
+growth_rate = BASE_RATE * reproduction_modifier * thermal_modifier * social_modifier
+
+BASE_RATE = 0.15  # turns^-1, tunable constant
+
+reproduction_modifier:
+  r_strategy → 2.0  (fast breeders)
+  k_strategy → 0.5  (slow breeders)
+
+thermal_modifier:
+  warm_blooded → 1.0  (constant activity)
+  cold_blooded → biome_temp_match(tile.temp, species.preferred_range)
+    # 1.0 if temp in preferred range, decays linearly to 0.3 at range edges
+
+social_modifier:
+  solitary → 1.0
+  pack     → 0.9   (slightly slower — fewer offspring per individual)
+  herd     → 1.1   (safety increases survival of young)
+  swarm    → 1.5   (rapid reproduction is the swarm strategy)
+  colony   → 1.2   (colonial organisms reproduce efficiently)
+```
+
+### Carrying Capacity Derivation
+
+```
+carrying_capacity = BASE_CAPACITY * size_modifier * biome_fauna_capacity * flora_density_factor
+
+BASE_CAPACITY = 100  # individuals per tile at baseline
+
+size_modifier:
+  tiny  → 5.0   (500 tiny creatures per tile)
+  small → 3.0   (300 small creatures)
+  medium → 1.0  (100 medium creatures)
+  large → 0.4   (40 large creatures)
+  huge  → 0.15  (15 huge creatures)
+
+biome_fauna_capacity:
+  From biomes.json fauna_capacity field (0.1 for polar_desert, 1.0 for temperate_forest)
+
+flora_density_factor:
+  For herbivores: canopy_cover * 0.5 + undergrowth * 0.5 (clamped to [0.2, 1.5])
+  For carnivores: 1.0 (independent of flora, depends on prey availability)
+  For detritivores: fungi_network * 1.5 (clamped to [0.3, 1.5])
+```
+
+### Death Rate
+
+```
+death_rate = BASE_DEATH * age_factor * starvation_factor
+
+BASE_DEATH = 0.05  # turns^-1, natural mortality
+
+age_factor:
+  1.0 if age < 80% of max_age
+  Linearly increases to 3.0 at max_age (old age mortality)
+
+starvation_factor:
+  1.0 if food_ratio >= 0.5
+  Linearly increases to 5.0 as food_ratio → 0 (starvation cascade)
+```
+
+---
+
+## Lotka-Volterra with Substeps
+
+The population dynamics use a modified Lotka-Volterra model with Holling Type II functional response, computed in 4 substeps per turn to prevent discrete-timestep instability.
+
+### Why Substeps
+
+Without substeps, a single predation calculation can consume more prey than exists (negative populations) or cause predator population to spike unrealistically. Substeps make the discrete simulation approximate continuous dynamics.
+
+**4 substeps** is the minimum that prevents instability across all tested biome configurations. Testing showed:
+- 1 substep: frequent extinctions in high-diversity biomes (tropical_rainforest)
+- 2 substeps: occasional extinctions in predator-rich biomes (deep_ocean)
+- 4 substeps: stable across all biomes
+- 8 substeps: marginal improvement not worth the compute cost
+
+### Holling Type II Functional Response
+
+```
+consumed = predation_rate * predator_pop * prey_pop / (prey_pop + half_saturation)
+```
+
+The `half_saturation` constant determines predator efficiency:
+- Low half_saturation (10): predators are very efficient, prey crashes quickly
+- High half_saturation (100): predators saturate, prey survives in large numbers
+
+**Tuning target**: `half_saturation = 0.5 * carrying_capacity` for the prey species. This produces realistic predator-prey oscillations that dampen over time.
+
+### Stochastic Noise
+
+Each substep includes +-5% hash-based noise:
+```
+noise = hash_noise(seed, tile, species, turn, substep) * 0.05
+```
+
+This prevents synchronized population crashes across tiles (where all populations hit minimum simultaneously). Deterministic from seed for reproducibility.
+
+---
+
+## Tuning Methodology
+
+### Phase 1: Single-Biome Isolation Tests
+
+Test each biome in isolation (single tile, closed system — no migration) for 200 turns:
+
+1. Generate species for the biome on 10 seeds
+2. Initialize populations at 50% carrying capacity
+3. Run 200 turns with no external inputs
+4. Record population curves every turn
+5. Verify:
+   - No species goes to zero by turn 200
+   - Population variance < 30% of mean over turns 100-200 (relaxed from 20% for single-tile)
+   - Food web pyramid holds at turn 200
+
+**If a biome fails**: Adjust biome-specific constants:
+- Increase producer growth_rate if herbivores crash (bottom-up starvation)
+- Decrease predation_rate if prey crashes (top-down overconsumption)
+- Increase half_saturation if oscillations don't dampen
+
+### Phase 2: Multi-Biome Map Tests
+
+Run 5 seeds on 60x40 maps for 200 turns:
+
+1. Use standard map generation (all biomes present through climate variation)
+2. Allow migration between tiles
+3. Record per-biome population aggregates every 10 turns
+4. Verify:
+   - No biome has zero total creatures at turn 200
+   - Global food web pyramid holds
+   - Migration fills gaps (some local extinctions OK, but biome-level populations persist)
+   - Population variance < 20% over turns 100-200
+
+**If a biome fails at map scale but passed in isolation**: Migration rates may be too low for that biome's species, or carrying capacity is too close to minimum viable population threshold.
+
+### Phase 3: Stress Tests
+
+Specific scenarios to verify robustness:
+
+| Test | Setup | Expected Outcome |
+|------|-------|-----------------|
+| Artificial extinction | Remove all creatures from one tile | Recolonized from neighbors within 20 turns |
+| Quality mismatch | Place Q5 creature on Q2 tile | Population declines, migrates within 10 turns |
+| Deforestation shock | Set canopy to 0 on a forest tile | Herbivore crash → predator crash → slow recovery as flora regrows |
+| Climate shift | Raise temperature 0.1 on a temperate tile | Gradual species turnover, no mass death event |
+| Predator removal | Remove all predators from a biome region | Herbivore explosion → overgrazing → flora crash → herbivore crash (trophic cascade) |
+
+---
+
+## Population Curve Analysis
+
+### What Healthy Curves Look Like
+
+**Producers**: Oscillate around 70-90% of carrying capacity. Dips from herbivore pressure, recovery when herbivores decline. Should stabilize with < 15% amplitude oscillations by turn 100.
+
+**Herbivores**: Classic predator-prey lag. Population peaks ~5-10 turns after producer peak. Dips when predators respond. Equilibrium around 40-60% of carrying capacity.
+
+**Predators**: Most volatile. Population peaks ~5-10 turns after herbivore peak. Sharp declines when prey is consumed. Equilibrium around 20-30% of carrying capacity. Largest oscillation amplitude, but must still dampen.
+
+### Warning Signs
+
+| Pattern | Indicates | Fix |
+|---------|----------|-----|
+| Predator population > herbivore | Predation rate too low or predator growth too high | Increase predation_rate or decrease predator growth_rate |
+| Producer crashes to near-zero | Herbivore grazing pressure too high | Decrease herbivore consumption_rate or increase producer growth_rate |
+| Oscillations growing (divergent) | System is unstable | Increase half_saturation, increase substeps, or decrease growth rates |
+| All populations flat (no oscillation) | Dynamics are over-dampened | Decrease half_saturation to make predators more responsive |
+| One species dominates, others extinct | Competitive exclusion | Adjust niche differentiation (trait-based carrying capacity differences) |
+| Population hits 0 then stays at 0 | Extinction is absorbing — migration didn't save it | Lower min_viable_population threshold or increase migration_range |
+
+### Recording Format
+
+Population data is recorded as JSON for analysis:
+
+```json
+{
+  "seed": 42,
+  "map_size": [60, 40],
+  "snapshots": [
+    {
+      "turn": 0,
+      "biomes": {
+        "temperate_forest": {
+          "tile_count": 145,
+          "total_creatures": 2340,
+          "by_trophic": {"producer": 1200, "herbivore": 800, "predator": 340},
+          "by_quality": {"Q1": 900, "Q2": 800, "Q3": 450, "Q4": 150, "Q5": 40},
+          "species_count": 12,
+          "births": 0,
+          "deaths": 0,
+          "migrations": 0,
+          "extinctions": 0
+        }
+      }
+    }
+  ]
+}
+```
+
+Snapshots taken every 10 turns (turns 0, 10, 20, ... 200) = 21 snapshots per seed, 5 seeds = 105 total snapshots.
+
+---
+
+## Food Web Pyramid Verification
+
+The ecological pyramid must hold at equilibrium: producer biomass > herbivore biomass > predator biomass.
+
+### Biomass Calculation
+
+```
+biomass(species) = population * SIZE_BIOMASS[species.size]
+
+SIZE_BIOMASS:
+  tiny   → 0.01
+  small  → 0.1
+  medium → 1.0
+  large  → 5.0
+  huge   → 20.0
+```
+
+### Verification
+
+For each biome at turns 100-200:
+```
+producer_biomass = sum(biomass for all producer species in biome)
+herbivore_biomass = sum(biomass for all herbivore + omnivore species)
+predator_biomass = sum(biomass for all carnivore species)
+
+assert producer_biomass > herbivore_biomass
+assert herbivore_biomass > predator_biomass
+```
+
+**Exception**: Aquatic biomes with filter feeders may have flatter pyramids (filter feeders are very efficient at converting producer biomass). The pyramid ratio (producer:herbivore) may be as low as 1.2:1 in coral_reef and shallow_ocean. Land biomes should maintain at least 2:1.
+
+**Detritivores** are excluded from the pyramid calculation — they recycle dead matter and exist outside the standard trophic chain.
+
+---
+
+## Tuning Constants Summary
+
+All tunable constants collected for reference. These are the knobs Block 3 will adjust:
+
+| Constant | Default | Range | Effect |
+|----------|---------|-------|--------|
+| `BASE_RATE` | 0.15 | 0.05-0.30 | Global growth speed |
+| `BASE_CAPACITY` | 100 | 50-200 | Global population ceiling |
+| `BASE_DEATH` | 0.05 | 0.02-0.10 | Natural mortality rate |
+| `SUBSTEPS` | 4 | 2-8 | Simulation resolution |
+| `half_saturation` | 0.5 * capacity | 0.2-0.8 * capacity | Predator efficiency |
+| `predation_rate` | 0.3 | 0.1-0.5 | How fast predators consume prey |
+| `grazing_rate` | 0.1 | 0.05-0.2 | Herbivore pressure on flora |
+| `min_viable_population` | 0.15 * capacity | 0.05-0.25 * capacity | Migration trigger threshold |
+| `noise_amplitude` | 0.05 | 0.01-0.10 | Stochastic variation |
+| `migration_range` | by locomotion | 1-5 tiles | How far species can migrate |
+| `stability_margin` | 0.05 | 0.02-0.10 | Biome reclassification hysteresis |
+
+### Per-Biome Overrides
+
+Some biomes need non-default constants:
+
+| Biome | Override | Reason |
+|-------|---------|--------|
+| `polar_desert` | BASE_CAPACITY * 0.1 | Extreme environment, very few creatures |
+| `deep_ocean` | half_saturation * 1.5 | Large predators need more prey saturation |
+| `tropical_rainforest` | BASE_CAPACITY * 1.3 | Peak terrestrial biodiversity |
+| `coral_reef` | BASE_CAPACITY * 1.5, grazing_rate * 0.5 | High density, coral is resilient producer |
+| `desert` | BASE_CAPACITY * 0.3, BASE_RATE * 0.7 | Low density, slow ecology |
+| `subterranean` | BASE_CAPACITY * 0.4, migration_range - 1 | Limited space, restricted movement |
+| `permanent_ice` | BASE_CAPACITY * 0.05 | Near-zero life support |
+| `pond` | BASE_CAPACITY * 0.2 | Tiny ecosystem |
diff --git a/games/age-of-dwarves/docs/design/SPECIES_TRAIT_CATALOG.md b/games/age-of-dwarves/docs/design/SPECIES_TRAIT_CATALOG.md
new file mode 100644
index 00000000..4bc5be80
--- /dev/null
+++ b/games/age-of-dwarves/docs/design/SPECIES_TRAIT_CATALOG.md
@@ -0,0 +1,548 @@
+# Species Trait Catalog
+
+> Complete trait system specification for trait-based species generation. Replaces M2a's partial SPECIES_TRAITS.md.
+
+---
+
+## 7 Trait Categories
+
+Every species is defined by exactly 7 traits. The combination determines biology, behavior, food web position, quality tier, and visual identity.
+
+### 1. Size
+
+| Value | Carrying Capacity Modifier | Quality Base | Notes |
+|-------|---------------------------|-------------|-------|
+| `tiny` | 5.0x | 1 | Insects, plankton, worms |
+| `small` | 3.0x | 2 | Rabbits, small fish, rodents |
+| `medium` | 1.0x | 3 | Deer, wolves, standard trees |
+| `large` | 0.4x | 4 | Bears, sharks, giant eagles |
+| `huge` | 0.15x | 5 | Whales, megafauna, ancient leviathans |
+
+### 2. Diet
+
+| Value | Trophic Level | Quality Modifier | Notes |
+|-------|--------------|-----------------|-------|
+| `producer` | 0 | -1 | Plants, algae, phytoplankton. Not fauna — flora proxy in food web |
+| `herbivore` | 1 | 0 | Grazes on producers, exerts grazing pressure |
+| `omnivore` | 1.5 | 0 | Eats producers AND smaller fauna |
+| `carnivore` | 2 | +1 | Eats fauna of strictly smaller size (pack bonus: +1 size tier) |
+| `detritivore` | 0.5 | -1 | Recycles dead matter, needs no live prey |
+| `filter_feeder` | 1 | 0 | Aquatic only. Eats tiny aquatic producers |
+
+### 3. Habitat
+
+| Value | Valid Substrates | Notes |
+|-------|-----------------|-------|
+| `terrestrial` | lowland, midland, highland, mountain, peak, wetland | Standard land species |
+| `aquatic` | deep_water, shallow_water, lake_bed | Water-only species |
+| `amphibious` | Any water OR adjacent-to-water land tile | Can exist on both. M2b addition: migrate across land-water boundary |
+| `aerial` | Any land substrate | Flying species. Can migrate seasonally (M2b) |
+| `subterranean` | mountain, peak (with cave marker) | Cave species. M2b addition |
+| `arboreal` | lowland, midland, highland (requires canopy > 0.3) | Tree-dwelling. Loses habitat if deforested |
+
+### 4. Locomotion
+
+| Value | Movement Range | Migration Range | Notes |
+|-------|---------------|----------------|-------|
+| `sessile` | 0 | 0 | Rooted. Coral, anemone, barnacle |
+| `walking` | 1 | 2 | Standard terrestrial movement |
+| `swimming` | 1 | 3 | Aquatic movement |
+| `flying` | 2 | 5 | Aerial. Highest migration range |
+| `burrowing` | 1 | 1 | Underground movement. Required for subterranean habitat |
+| `climbing` | 1 | 2 | Cave walls, cliff faces. M2b addition for subterranean |
+| `slithering` | 1 | 2 | Snakes, worms. Low movement cost through undergrowth |
+
+### 5. Reproduction
+
+| Value | Growth Rate Modifier | Litter Size | Quality Modifier | Notes |
+|-------|---------------------|-------------|-----------------|-------|
+| `r_strategy` | 2.0x | 3-8 | -1 | Fast breeders, many offspring, high mortality |
+| `k_strategy` | 0.5x | 1-2 | 0 | Slow breeders, few offspring, high parental investment |
+
+### 6. Thermal
+
+| Value | Climate Tolerance | Activity | Notes |
+|-------|------------------|---------|-------|
+| `cold_blooded` | Narrow temp range (biome-specific) | Reduced in cold | Reptiles, insects, fish |
+| `warm_blooded` | Wide temp range | Constant | Mammals, birds. Higher food requirement |
+
+### 7. Social
+
+| Value | Group Size | Hunting Modifier | Notes |
+|-------|-----------|-----------------|-------|
+| `solitary` | 1 | 1.0x | Lone hunters/grazers |
+| `pack` | 3-6 | 1.5x (can prey +1 size tier) | Coordinated hunters |
+| `herd` | 10-30 | 0.8x | Safety in numbers, defensive bonus |
+| `swarm` | 50-200 | 0.5x per individual, collective 5.0x | Insects, bats. Tiny/small only |
+| `colony` | 20-100 | n/a (sessile or burrowing) | Ants, coral, cave insects |
+
+---
+
+## Subterranean Additions (M2b)
+
+### New Locomotion Value: `climbing`
+
+Cave-wall climbing for species that traverse vertical cave surfaces. Required alongside `burrowing` for full subterranean mobility.
+
+### Visual Mode Sub-traits
+
+These are flavor properties attached to subterranean species by FlavorGenerator, not gameplay traits. They affect sprite prompts and names only.
+
+| Visual Mode | Description | Prompt Keywords |
+|-------------|-------------|----------------|
+| `blind` | No functional eyes. Relies on other senses | eyeless, smooth face, no eye sockets, vestigial eye bumps |
+| `echolocation` | Bat-like sonar sensing | large ears, flattened nose, wide mouth, ultrasonic |
+| `bioluminescent` | Self-illuminating organs | glowing spots, phosphorescent markings, light organs, eerie glow |
+
+Species in the subterranean biome are assigned 1-2 visual modes probabilistically:
+
+| Visual Mode | Weight in Subterranean | Can Combine With |
+|-------------|----------------------|-----------------|
+| `blind` | 0.50 | echolocation, bioluminescent |
+| `echolocation` | 0.30 | blind, bioluminescent |
+| `bioluminescent` | 0.40 | blind, echolocation |
+
+### Subterranean Flavor Additions
+
+**Prefixes** (added to `flavor.json` subterranean biome entry):
+Pale, Crystal, Cave, Blind, Hollow, Deepstone, Gloom, Vein, Fungal, Phosphor
+
+**Motifs**:
+- translucent skin revealing internal structures
+- crystalline growths on carapace or hide
+- eyeless smooth face
+- oversized ears or antennae
+- pheromone sacs (colony species)
+- bioluminescent markings along body
+- pallid coloration (white, grey, translucent pink)
+- elongated limbs adapted for cave traversal
+
+---
+
+## 9 Trait Constraints (Invalid Combinations)
+
+| # | Constraint | Reason |
+|---|-----------|--------|
+| 1 | `aquatic` + `burrowing` | Can't burrow through water |
+| 2 | `sessile` + `carnivore` | Rooted organisms can't hunt |
+| 3 | `aerial` + `huge` | Too heavy to fly |
+| 4 | `subterranean` + `aerial` | Can't fly underground |
+| 5 | `filter_feeder` + `terrestrial` | Filter feeding requires water |
+| 6 | `sessile` + `walking`/`flying`/`swimming` | Sessile means immobile |
+| 7 | `arboreal` + `aquatic` | Can't be in trees and water simultaneously |
+| 8 | `swarm` + `huge` | Ecological impossibility, breaks carrying capacity |
+| 9 | `sessile` + non-`colony` social | Sessile organisms only form colonies |
+
+Additional M2b constraints:
+
+| # | Constraint | Reason |
+|---|-----------|--------|
+| 10 | `climbing` + `aquatic` | Climbing is for cave walls, not water |
+| 11 | `climbing` + `aerial` | Flyers don't need to climb |
+| 12 | `subterranean` + `arboreal` | No trees underground |
+| 13 | `subterranean` + `herd` | Caves are too confined for herds |
+
+---
+
+## Per-Biome Trait Weight Summaries
+
+Weights are relative probabilities (0.0-1.0) for SpeciesGenerator. Each biome generates species with trait distributions appropriate to its ecology.
+
+### Aquatic Biomes
+
+#### deep_ocean
+
+| Trait | High Weight (>0.5) | Medium (0.2-0.5) | Low (<0.2) |
+|-------|--------------------|-------------------|------------|
+| size | huge (0.3), large (0.3) | medium (0.25) | small (0.1), tiny (0.05) |
+| diet | carnivore (0.4) | filter_feeder (0.25), herbivore (0.15) | omnivore (0.1), detritivore (0.1) |
+| habitat | aquatic (1.0) | | |
+| locomotion | swimming (0.9) | | sessile (0.1) |
+| reproduction | k_strategy (0.6) | r_strategy (0.4) | |
+| thermal | cold_blooded (0.7) | warm_blooded (0.3) | |
+| social | solitary (0.5) | pack (0.2), herd (0.2) | swarm (0.1) |
+
+#### shallow_ocean
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | small (0.3), medium (0.3) | large (0.2) | tiny (0.15), huge (0.05) |
+| diet | herbivore (0.3), carnivore (0.25) | omnivore (0.2), filter_feeder (0.15) | detritivore (0.1) |
+| habitat | aquatic (1.0) | | |
+| locomotion | swimming (0.85) | | sessile (0.15) |
+| reproduction | r_strategy (0.55) | k_strategy (0.45) | |
+| thermal | cold_blooded (0.6) | warm_blooded (0.4) | |
+| social | herd (0.3), solitary (0.3) | pack (0.2) | swarm (0.1), colony (0.1) |
+
+#### coral_reef
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | tiny (0.3), small (0.4) | medium (0.2) | large (0.08), huge (0.02) |
+| diet | herbivore (0.3), omnivore (0.25) | carnivore (0.2), filter_feeder (0.15) | detritivore (0.1) |
+| habitat | aquatic (1.0) | | |
+| locomotion | swimming (0.7) | sessile (0.3) | |
+| reproduction | r_strategy (0.7) | k_strategy (0.3) | |
+| thermal | cold_blooded (0.9) | warm_blooded (0.1) | |
+| social | colony (0.3), herd (0.25) | swarm (0.2), solitary (0.15) | pack (0.1) |
+
+#### estuary
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | small (0.35), medium (0.3) | tiny (0.15), large (0.15) | huge (0.05) |
+| diet | omnivore (0.3), herbivore (0.25) | carnivore (0.2), detritivore (0.15) | filter_feeder (0.1) |
+| habitat | amphibious (0.4), aquatic (0.4) | | aerial (0.2) |
+| locomotion | swimming (0.5) | walking (0.25), flying (0.15) | slithering (0.1) |
+| reproduction | r_strategy (0.6) | k_strategy (0.4) | |
+| thermal | cold_blooded (0.55) | warm_blooded (0.45) | |
+| social | herd (0.3), solitary (0.25) | pack (0.2), colony (0.15) | swarm (0.1) |
+
+#### pond
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | tiny (0.5), small (0.35) | | medium (0.15) |
+| diet | herbivore (0.3), detritivore (0.25) | omnivore (0.25) | carnivore (0.15), filter_feeder (0.05) |
+| habitat | aquatic (0.5), amphibious (0.3) | | aerial (0.2) |
+| locomotion | swimming (0.5) | walking (0.2), flying (0.2) | slithering (0.1) |
+| reproduction | r_strategy (0.8) | k_strategy (0.2) | |
+| thermal | cold_blooded (0.7) | warm_blooded (0.3) | |
+| social | swarm (0.3), colony (0.25) | solitary (0.25) | herd (0.1), pack (0.1) |
+
+#### river
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | small (0.4), medium (0.3) | tiny (0.15) | large (0.12), huge (0.03) |
+| diet | herbivore (0.25), omnivore (0.25) | carnivore (0.25) | detritivore (0.15), filter_feeder (0.1) |
+| habitat | aquatic (0.5), amphibious (0.3) | | aerial (0.2) |
+| locomotion | swimming (0.6) | walking (0.15), flying (0.15) | slithering (0.1) |
+| reproduction | r_strategy (0.6) | k_strategy (0.4) | |
+| thermal | cold_blooded (0.5) | warm_blooded (0.5) | |
+| social | solitary (0.3), herd (0.25) | pack (0.2) | swarm (0.15), colony (0.1) |
+
+#### lake
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | small (0.35), medium (0.3) | tiny (0.15), large (0.15) | huge (0.05) |
+| diet | herbivore (0.25), omnivore (0.25) | carnivore (0.2), filter_feeder (0.15) | detritivore (0.15) |
+| habitat | aquatic (0.6), amphibious (0.25) | | aerial (0.15) |
+| locomotion | swimming (0.65) | walking (0.15), flying (0.1) | slithering (0.1) |
+| reproduction | r_strategy (0.55) | k_strategy (0.45) | |
+| thermal | cold_blooded (0.55) | warm_blooded (0.45) | |
+| social | herd (0.3), solitary (0.25) | pack (0.2) | swarm (0.15), colony (0.1) |
+
+#### mangrove
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | small (0.35), medium (0.3) | tiny (0.15), large (0.15) | huge (0.05) |
+| diet | omnivore (0.3), carnivore (0.25) | herbivore (0.2), detritivore (0.15) | filter_feeder (0.1) |
+| habitat | amphibious (0.5), aquatic (0.2) | arboreal (0.15) | aerial (0.15) |
+| locomotion | swimming (0.3), walking (0.25) | climbing (0.2), flying (0.15) | slithering (0.1) |
+| reproduction | r_strategy (0.6) | k_strategy (0.4) | |
+| thermal | cold_blooded (0.65) | warm_blooded (0.35) | |
+| social | solitary (0.3), colony (0.25) | pack (0.2) | swarm (0.15), herd (0.1) |
+
+### Tropical Biomes
+
+#### tropical_rainforest
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | medium (0.3), small (0.25) | large (0.2), tiny (0.15) | huge (0.1) |
+| diet | herbivore (0.25), omnivore (0.25) | carnivore (0.2), detritivore (0.15) | producer (0.1), filter_feeder (0.05) |
+| habitat | arboreal (0.35), terrestrial (0.35) | | aerial (0.2), amphibious (0.1) |
+| locomotion | climbing (0.3), walking (0.25) | flying (0.2) | slithering (0.15), burrowing (0.1) |
+| reproduction | r_strategy (0.5) | k_strategy (0.5) | |
+| thermal | warm_blooded (0.5) | cold_blooded (0.5) | |
+| social | solitary (0.25), pack (0.2) | herd (0.2), swarm (0.2) | colony (0.15) |
+
+#### tropical_dry_forest
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | medium (0.3), small (0.3) | large (0.2) | tiny (0.1), huge (0.1) |
+| diet | herbivore (0.3), omnivore (0.25) | carnivore (0.2) | detritivore (0.15), producer (0.1) |
+| habitat | terrestrial (0.45), arboreal (0.25) | | aerial (0.2), amphibious (0.1) |
+| locomotion | walking (0.35), climbing (0.2) | flying (0.2) | slithering (0.15), burrowing (0.1) |
+| reproduction | r_strategy (0.55) | k_strategy (0.45) | |
+| thermal | warm_blooded (0.45) | cold_blooded (0.55) | |
+| social | herd (0.25), solitary (0.25) | pack (0.2) | swarm (0.15), colony (0.15) |
+
+#### savanna
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | large (0.3), medium (0.3) | small (0.2) | huge (0.1), tiny (0.1) |
+| diet | herbivore (0.35), carnivore (0.25) | omnivore (0.2) | detritivore (0.1), producer (0.1) |
+| habitat | terrestrial (0.7) | | aerial (0.2), amphibious (0.1) |
+| locomotion | walking (0.6) | flying (0.2) | burrowing (0.1), slithering (0.1) |
+| reproduction | k_strategy (0.5) | r_strategy (0.5) | |
+| thermal | warm_blooded (0.6) | cold_blooded (0.4) | |
+| social | herd (0.35), pack (0.25) | solitary (0.2) | swarm (0.1), colony (0.1) |
+
+#### desert
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | small (0.35), tiny (0.3) | medium (0.2) | large (0.1), huge (0.05) |
+| diet | omnivore (0.3), carnivore (0.25) | herbivore (0.2), detritivore (0.15) | producer (0.1) |
+| habitat | terrestrial (0.7) | subterranean (0.15) | aerial (0.15) |
+| locomotion | walking (0.3), burrowing (0.25) | slithering (0.25) | flying (0.15), climbing (0.05) |
+| reproduction | r_strategy (0.65) | k_strategy (0.35) | |
+| thermal | cold_blooded (0.7) | warm_blooded (0.3) | |
+| social | solitary (0.45), colony (0.2) | pack (0.15) | swarm (0.15), herd (0.05) |
+
+### Temperate Biomes
+
+#### temperate_forest
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | medium (0.3), small (0.25) | large (0.2) | tiny (0.1), huge (0.15) |
+| diet | herbivore (0.3), omnivore (0.25) | carnivore (0.2) | detritivore (0.15), producer (0.1) |
+| habitat | terrestrial (0.5), arboreal (0.2) | | aerial (0.2), amphibious (0.1) |
+| locomotion | walking (0.4) | climbing (0.2), flying (0.2) | burrowing (0.1), slithering (0.1) |
+| reproduction | k_strategy (0.5) | r_strategy (0.5) | |
+| thermal | warm_blooded (0.65) | cold_blooded (0.35) | |
+| social | solitary (0.25), pack (0.25) | herd (0.2) | colony (0.15), swarm (0.15) |
+
+#### temperate_grassland
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | medium (0.3), small (0.25) | large (0.2) | tiny (0.1), huge (0.15) |
+| diet | herbivore (0.35), carnivore (0.25) | omnivore (0.2) | detritivore (0.1), producer (0.1) |
+| habitat | terrestrial (0.7) | | aerial (0.2), amphibious (0.1) |
+| locomotion | walking (0.5) | flying (0.2), burrowing (0.15) | slithering (0.1), climbing (0.05) |
+| reproduction | r_strategy (0.5) | k_strategy (0.5) | |
+| thermal | warm_blooded (0.6) | cold_blooded (0.4) | |
+| social | herd (0.35), pack (0.25) | solitary (0.2) | swarm (0.1), colony (0.1) |
+
+#### chaparral
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | small (0.35), medium (0.3) | tiny (0.15) | large (0.15), huge (0.05) |
+| diet | omnivore (0.3), herbivore (0.25) | carnivore (0.2) | detritivore (0.15), producer (0.1) |
+| habitat | terrestrial (0.7) | | aerial (0.15), subterranean (0.15) |
+| locomotion | walking (0.35), burrowing (0.2) | slithering (0.2) | flying (0.15), climbing (0.1) |
+| reproduction | r_strategy (0.6) | k_strategy (0.4) | |
+| thermal | cold_blooded (0.55) | warm_blooded (0.45) | |
+| social | solitary (0.35), pack (0.2) | colony (0.2) | herd (0.15), swarm (0.1) |
+
+#### swamp
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | medium (0.3), small (0.25) | large (0.2), tiny (0.15) | huge (0.1) |
+| diet | omnivore (0.25), carnivore (0.25) | herbivore (0.2), detritivore (0.2) | filter_feeder (0.1) |
+| habitat | amphibious (0.4), terrestrial (0.3) | | aquatic (0.15), aerial (0.15) |
+| locomotion | swimming (0.3), walking (0.25) | slithering (0.2) | flying (0.15), burrowing (0.1) |
+| reproduction | r_strategy (0.6) | k_strategy (0.4) | |
+| thermal | cold_blooded (0.6) | warm_blooded (0.4) | |
+| social | solitary (0.3), colony (0.2) | swarm (0.2), pack (0.15) | herd (0.15) |
+
+#### bog
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | tiny (0.35), small (0.35) | medium (0.2) | large (0.08), huge (0.02) |
+| diet | detritivore (0.3), herbivore (0.25) | omnivore (0.2) | carnivore (0.15), filter_feeder (0.1) |
+| habitat | amphibious (0.35), terrestrial (0.35) | | aerial (0.2), aquatic (0.1) |
+| locomotion | walking (0.25), swimming (0.2) | flying (0.2), burrowing (0.15) | slithering (0.15), climbing (0.05) |
+| reproduction | r_strategy (0.7) | k_strategy (0.3) | |
+| thermal | cold_blooded (0.6) | warm_blooded (0.4) | |
+| social | swarm (0.3), colony (0.25) | solitary (0.2) | herd (0.15), pack (0.1) |
+
+### Cold Biomes
+
+#### boreal_forest
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | medium (0.3), large (0.25) | small (0.2) | huge (0.15), tiny (0.1) |
+| diet | herbivore (0.3), carnivore (0.25) | omnivore (0.25) | detritivore (0.1), producer (0.1) |
+| habitat | terrestrial (0.6) | arboreal (0.15) | aerial (0.15), amphibious (0.1) |
+| locomotion | walking (0.5) | climbing (0.15), flying (0.15) | burrowing (0.1), slithering (0.1) |
+| reproduction | k_strategy (0.55) | r_strategy (0.45) | |
+| thermal | warm_blooded (0.75) | cold_blooded (0.25) | |
+| social | pack (0.3), solitary (0.25) | herd (0.2) | colony (0.15), swarm (0.1) |
+
+#### tundra
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | large (0.3), medium (0.3) | small (0.2) | huge (0.1), tiny (0.1) |
+| diet | herbivore (0.35), carnivore (0.25) | omnivore (0.2) | detritivore (0.15), producer (0.05) |
+| habitat | terrestrial (0.8) | | aerial (0.15), amphibious (0.05) |
+| locomotion | walking (0.6) | flying (0.2) | burrowing (0.1), slithering (0.05), climbing (0.05) |
+| reproduction | k_strategy (0.6) | r_strategy (0.4) | |
+| thermal | warm_blooded (0.85) | cold_blooded (0.15) | |
+| social | herd (0.4), pack (0.25) | solitary (0.2) | colony (0.1), swarm (0.05) |
+
+#### polar_desert
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | medium (0.3), small (0.3) | large (0.2) | tiny (0.15), huge (0.05) |
+| diet | carnivore (0.3), herbivore (0.25) | omnivore (0.2) | detritivore (0.15), filter_feeder (0.1) |
+| habitat | terrestrial (0.5), aquatic (0.3) | | amphibious (0.2) |
+| locomotion | walking (0.35), swimming (0.3) | | flying (0.15), burrowing (0.1), slithering (0.1) |
+| reproduction | k_strategy (0.65) | r_strategy (0.35) | |
+| thermal | warm_blooded (0.9) | cold_blooded (0.1) | |
+| social | herd (0.3), solitary (0.3) | pack (0.2) | colony (0.15), swarm (0.05) |
+
+### Elevation Biomes
+
+#### montane_forest
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | medium (0.3), large (0.25) | small (0.2) | huge (0.15), tiny (0.1) |
+| diet | herbivore (0.3), omnivore (0.25) | carnivore (0.2) | detritivore (0.15), producer (0.1) |
+| habitat | terrestrial (0.5), arboreal (0.2) | | aerial (0.2), amphibious (0.1) |
+| locomotion | walking (0.35), climbing (0.25) | flying (0.2) | burrowing (0.1), slithering (0.1) |
+| reproduction | k_strategy (0.55) | r_strategy (0.45) | |
+| thermal | warm_blooded (0.7) | cold_blooded (0.3) | |
+| social | solitary (0.3), pack (0.25) | herd (0.2) | colony (0.15), swarm (0.1) |
+
+#### cloud_forest
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | small (0.3), medium (0.3) | tiny (0.2) | large (0.15), huge (0.05) |
+| diet | herbivore (0.25), omnivore (0.25) | detritivore (0.2) | carnivore (0.15), producer (0.15) |
+| habitat | arboreal (0.4), terrestrial (0.3) | | aerial (0.2), amphibious (0.1) |
+| locomotion | climbing (0.35), flying (0.2) | walking (0.2) | slithering (0.15), burrowing (0.1) |
+| reproduction | r_strategy (0.5) | k_strategy (0.5) | |
+| thermal | warm_blooded (0.5) | cold_blooded (0.5) | |
+| social | solitary (0.3), colony (0.2) | swarm (0.2) | pack (0.15), herd (0.15) |
+
+#### alpine_meadow
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | medium (0.3), small (0.25) | large (0.2) | tiny (0.15), huge (0.1) |
+| diet | herbivore (0.4), omnivore (0.2) | carnivore (0.2) | detritivore (0.1), producer (0.1) |
+| habitat | terrestrial (0.7) | | aerial (0.25), amphibious (0.05) |
+| locomotion | walking (0.45), climbing (0.2) | flying (0.2) | burrowing (0.1), slithering (0.05) |
+| reproduction | k_strategy (0.55) | r_strategy (0.45) | |
+| thermal | warm_blooded (0.75) | cold_blooded (0.25) | |
+| social | herd (0.3), solitary (0.25) | pack (0.25) | colony (0.1), swarm (0.1) |
+
+#### alpine_tundra
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | medium (0.3), small (0.25) | large (0.2) | tiny (0.15), huge (0.1) |
+| diet | herbivore (0.35), carnivore (0.25) | omnivore (0.2) | detritivore (0.15), producer (0.05) |
+| habitat | terrestrial (0.8) | | aerial (0.15), subterranean (0.05) |
+| locomotion | walking (0.4), climbing (0.25) | flying (0.15) | burrowing (0.15), slithering (0.05) |
+| reproduction | k_strategy (0.6) | r_strategy (0.4) | |
+| thermal | warm_blooded (0.8) | cold_blooded (0.2) | |
+| social | herd (0.3), pack (0.25) | solitary (0.25) | colony (0.15), swarm (0.05) |
+
+#### permanent_ice
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | small (0.3), medium (0.3) | tiny (0.2) | large (0.15), huge (0.05) |
+| diet | carnivore (0.3), herbivore (0.25) | omnivore (0.2) | detritivore (0.15), producer (0.1) |
+| habitat | terrestrial (0.5), aquatic (0.3) | | amphibious (0.2) |
+| locomotion | walking (0.3), swimming (0.3) | | flying (0.15), climbing (0.15), burrowing (0.1) |
+| reproduction | k_strategy (0.7) | r_strategy (0.3) | |
+| thermal | warm_blooded (0.9) | cold_blooded (0.1) | |
+| social | herd (0.3), solitary (0.3) | pack (0.2) | colony (0.15), swarm (0.05) |
+
+### Subterranean Biome
+
+#### subterranean
+
+| Trait | High Weight | Medium | Low |
+|-------|-----------|---------|----|
+| size | small (0.35), tiny (0.3) | medium (0.2) | large (0.1), huge (0.05) |
+| diet | omnivore (0.25), detritivore (0.25) | carnivore (0.2), herbivore (0.15) | producer (0.1), filter_feeder (0.05) |
+| habitat | subterranean (0.8) | | amphibious (0.1), terrestrial (0.1) |
+| locomotion | burrowing (0.35), climbing (0.3) | walking (0.15) | slithering (0.15), swimming (0.05) |
+| reproduction | r_strategy (0.65) | k_strategy (0.35) | |
+| thermal | cold_blooded (0.75) | warm_blooded (0.25) | |
+| social | colony (0.35), swarm (0.2) | solitary (0.2) | pack (0.15), herd (0.1) |
+
+Typical generated species:
+- small + burrowing + cold_blooded + colony + omnivore = "cave insect-like"
+- medium + climbing + cold_blooded + solitary + carnivore = "giant spider-like"
+- small + flying + warm_blooded + swarm + carnivore = "bat-like"
+- tiny + burrowing + cold_blooded + colony + detritivore = "cave worm-like"
+- medium + swimming + cold_blooded + solitary + carnivore = "blind cave fish-like" (in flooded caves)
+
+---
+
+## Quality Tier Derivation
+
+### Formula
+
+```
+species_quality = clamp(base + modifiers, 1, 5)
+
+base = SIZE_QUALITY[size]
+  tiny   → 1
+  small  → 2
+  medium → 3
+  large  → 4
+  huge   → 5
+
+modifiers:
+  r_strategy    → -1
+  k_strategy    →  0
+  detritivore   → -1
+  carnivore     → +1
+```
+
+### Quality Range (species lifetime)
+
+Species don't stay at one quality. They have a quality range based on the derived base:
+
+| Derived Quality | Quality Range | Example |
+|----------------|-------------|---------|
+| Q1 | Q1-Q2 | Worms, algae, tiny insects |
+| Q2 | Q1-Q3 | Common fish, rabbits, cave insects |
+| Q3 | Q2-Q4 | Deer, wolves (young), standard predators |
+| Q4 | Q3-Q5 | Bears, sharks, dire wolves |
+| Q5 | Q4-Q5 | Ancient leviathans, megafauna |
+
+An individual creature spawns at `quality_range[0]` and ages up toward `quality_range[1]`, capped by `min(species.max_quality, tile.quality)`.
+
+---
+
+## Spawn Probability Table
+
+Tile quality gates which species quality tiers can spawn. Higher-quality tiles support rarer species.
+
+| Tile Quality | Q1 species | Q2 species | Q3 species | Q4 species | Q5 species |
+|-------------|-----------|-----------|-----------|-----------|-----------|
+| Q1 tile | 50% | 30% | 10% | 0% | 0% |
+| Q2 tile | 30% | 40% | 25% | 5% | 0% |
+| Q3 tile | 10% | 25% | 40% | 20% | 5% |
+| Q4 tile | 5% | 15% | 30% | 35% | 15% |
+| Q5 tile | 0% | 10% | 25% | 35% | 30% |
+
+Species can only spawn on tiles where `tile.quality >= species.min_quality`. The table above gives the probability of each quality tier being selected when the tile generates a new species.
+
+---
+
+## Minimum Species Per Biome
+
+After generation across 10 seeds, each biome must produce:
+
+| Trophic Level | Minimum Count | Rationale |
+|--------------|---------------|-----------|
+| Producer | 3 | Base of food web, must be diverse enough to support herbivores |
+| Herbivore | 3 | Multiple prey species prevent single-point food web collapse |
+| Predator | 2 | At least one solitary + one pack predator for ecological balance |
+| Detritivore | 1 | Recycler role, prevents dead-matter buildup |
+
+If any biome fails these minimums across the seed set, its trait weights need adjustment (increase weight for the underrepresented trophic level).