Cambrian Open World

Create a complete, self-contained HTML file for an open-world 3D exploration simulation set in a Cambrian-era ocean roughly 518 million years ago. The player should be able to roam an atmospheric seafloor and discover recognizable prehistoric organisms. This is an interactive experience, not a static illustration or informational landing page.

Core requirements:
- Single HTML file; Three.js may be loaded from unpkg or jsDelivr, with all other CSS and JavaScript inline
- Use a fixed default random seed of 518 for terrain, organism placement, and initial behavior. Restarting must reproduce the same initial world
- Initial state: start the player in the shallow reef with movement instructions visible, an empty discovery log, 180 seconds of expedition time, and an Anomalocaris visible in the middle distance
- A substantial underwater environment with uneven terrain, rocks, microbial mats, sponges, drifting particles, fog, caustic light, and a visible water surface above
- Five visually distinct organism models: Anomalocaris, Opabinia, Hallucigenia, Marrella, and trilobites. Their silhouettes must be recognizable from geometry rather than color alone
- At least three species must have meaningfully different animation or locomotion: Anomalocaris swims with lateral body motion, Opabinia swims and probes with its trunk, and trilobites or Hallucigenia crawl along the terrain rather than floating
- First-person or close third-person exploration using WASD or arrow keys and mouse controls, with clear movement instructions
- Click or approach an organism to identify it and open a compact field-guide card with its name, scale, diet, and one factual detail
- Identification invariant: approaching within roughly five body lengths or clicking an organism must identify it once, add exactly one entry to the discovery log, and open its field-guide card
- Predator-prey invariant: at least once per seeded run, Anomalocaris must detect and pursue a visible trilobite; the trilobite must flee, and the encounter must end in escape or capture rather than endless following
- Player-reaction invariant: when the player approaches within roughly five body lengths, at least two species must change behavior; one flees and another turns toward or investigates the player
- Three discoverable zones: shallow reef, sponge garden, and dark trench. Entering each zone must update its label, lighting, and local species mix, not only the fog color
- A small compass, depth readout, and functional expedition timer in the HUD. The timer starts at 180 seconds, pauses when the simulation is paused, reaches zero only through elapsed play time, and then shows an expedition summary with species discovered
- A polished loading screen and a graceful message if WebGL is unavailable

Stretch goal:
- Add usable touch movement and camera controls without weakening desktop keyboard and mouse controls

Favor atmosphere, exploration, and legible interaction over photorealism. Do not use modern fish, dinosaurs, or other organisms from the wrong geological period. Implement the observable behaviors above before adding decorative detail.