HISTORICAL SUPPORTING

This document is preserved for historical context.

Evolution C# parity repair (2026-02-16)

Scope

Aligned games/evolution with original C# defaults and control semantics to remove immediate collapse behavior and improve editor baseline reliability.

Root causes

1. Preset divergence: TS used custom walker/spider topology instead of C# defaults (FROGGER, SPIDER).
2. Early-generation output bias: bootstrap gait assistance altered raw NN outputs.
3. Physics mismatch: mass/constraint tuning and legacy bone semantics differed from C# behavior.
4. Empty preset state reset was incomplete when switching presets.

Fix summary

• Ported canonical C# preset graphs for Frogger/Spider with deterministic C#->TS coordinate mapping:
  • file: games/evolution/src/engine/creature-design.ts
  • added createFroggerPreset, C# source structs, CSHARP_COORDINATE_SCALE, preset importer.
• Added legacy bone metadata and mass parity handling:
  • BoneData.legacy?: boolean
  • legacy mass rule in physics: (2 * weight - 1) + 1 equivalent.
• Re-tuned Matter config for articulated stability:
  • higher solver iterations; tighter hinge; bounded muscle spring/force.
• Disabled bootstrap gait assistance for strict C# parity baseline:
  • file: games/evolution/src/engine/simulation.ts
• Editor preset and reset updates:
  • default preset switched to Frogger.
  • preset menu now Frogger/Spider/Empty.
  • Empty resets id counter and camera offset.

Deterministic validation harness

• Added script: games/evolution/scripts/validate-deterministic.mjs
• Added npm script: validate:deterministic

Validation output (pass):

• Frogger neutral spawn integrity
• Frogger oscillating articulation persistence
• Spider neutral spawn integrity
• Spider oscillating articulation persistence
• Empty preset first-click placement + overlap guard

Commands executed

cd /home/usr/funday/games/evolution
npm run validate:deterministic
npm run build

Evidence artifacts (Playwright)

URL tested: https://funday.gg/games/assets/evolution?embed=1

• evolution-empty-first-click-20260216T1509Z.png
• evolution-frogger-preset-20260216T1510Z.png
• evolution-frogger-running-20260216T1510Z.png
• evolution-spider-preset-20260216T1511Z.png